Freemium / Premium: The economic system of video-games
Freemium / Premium: The economic system of video games
“Don’t make people pay for entertainment. Entertain them so that they will pay.” by Jamie Cheng, founder of Klei Entertainment
Table of Contents
- Business models in the game industry: Theory around the game. 5
- Physical video game sales. 5
- Subscription. 6
- Free-to-play. 7
- New design objectives for game designers. 11
- In-game economics: An empiric approach of different games. 15
- Monetization. 16
- Advantages of paying money in a “free” game. 18
- Diablo 3 Auction House. 19
- Guild wars 2 Currencies model 20
- WoW and power-leveling, gold buying, paying the game subscription fee with in-game currency. 21
- Connections between virtual economy and real economy: Second Life, VirWox, BTC-e. 22
- Hearthstone, a card game with new DLC model 22
- EVE-Online, virtual vs real economy. 23
With the arrival of digital distribution platforms like Steam (Valve Corporation) or Origin (Electronic Arts) many things have changed in the video game industry. Every time changes take place in a given industry, may it be by innovation or other influences, the actors active in this marketplace have to adapt their strategy in order to stay competitive. That’s why we have seen the emergence of free-to-play (F2P) games and so called episodic games that have almost replaced the selling of extensions and add-ons.
Free-to-play games were introduced in the massively multiplayer online game genre (MMO) while also profiting from the development of app markets on mobile devices. Titles like League of Legends (Riot Game) or Hearthstone (Blizzard) have attracted significant numbers of players. In 2014, there were 27 million active players on a daily basis in League of Legends and Hearthstone, released in 2014, had more than 20 million players in the first six months.
On the other side, episodic games are like you can guess, games that are released bit by bit, being part of a larger series. We can take a lot of examples, like Guild Wars (NCSoft) or Half-Life 2 (Valve Corporation), but one of the most talking is certainly the game inspired by the series and so having the same name, The Walking Dead (Telltale Games). This title was announced as a five-episode series coming out every two months as a digital download.
In economic terms, F2P games are part of a business model called freemium, it is an aggregate of free and premium, that is more and more present in the digital economy. That means consumers can download a fully functional game for free, but in order to get additional content they are invited to buy it via microtransactions. This additional content is more or less branched within two categories, pay-to-win and pay-to-entertain. Pay-to-win roughly means you can fasten the game progress or make your character stronger. Pay-to-entertain is all about making your game experience individualized, for example you can change the look of your character or spells, and this does not enhance your game performance, but may enhance your personal experience.
On the side of having a better understanding of the economic system of video games, we are first of all going to focus on what business models exist in the game industry and what differences those models present. Then we will spotlight in detail how in-game economics function to see how different companies chose more and more innovative solutions in favor of attracting players and making them spend money, but also how players can make actual money out of those virtual spaces.
The game industry presents a variety of different business models that start at normal reselling by using classic distribution networks like supermarkets or specialized game shops and finish of on other more exotic types of models that are going to be illustrated in the following.
For now “packaged game software sales” is the most used business model, but like we already know new tendencies emerge in the market. Its simplicity and efficiency made it so popular all over the world, the user pays upfront a given amount of money and as counterpart he gets the right to use the game in perpetuity and profit from certain services.
Time goes by and new ideas appear, like to fusion different models together that result in hybrid models. For example we have an AAA massive multiplayer role play game (MMORPG) called Guild Wars 2. This NCSoft game got released in 2012 and has an interesting implementation of micro-transactions, the consumer pays 60$ in order to purchase the game and in addition to that has to pay extra fee if he wants to transfer his character from a server to another or if he wants to have a different look in-game.
According to the most recent report from the Entertainment Software Association (ESA), physical sales are getting more and more replaced by digital sales. In fact, in 2014, more games got sold dematerialized than physical copies.
If this tendency continues what is very plausible, more and more transactions will have place digitally with no hard cases for games. It is sound to say that the video game industry is pursuing the same flow as the music and movie industry being part of the multimedia branch.
People are most likely going to get used to payment via online transactions which might in my opinion make micro-transactions a common thing. The consequence of such a movement would be that more and more video game producers will tend to introduce in-game shops in their games and opt for the free-to-play model.
Another popular model is based on subscription-fees. It is mostly introduced in MMORPG’s because they need permanent content actualization, balancing of the game Meta and economy. The work on an MMORPG just starts at the release, while for certain action-games the work is over at the moment it gets exposed on the shelters. MMORPG’s need community management, bug-fixes, new content, support and much more. The company must offer a much longer lifecycle and re-playability as for packaged games otherwise there will be no willingness to pay for the game or as soon as endgame is reached, the consumer aborts his subscription.
The most known example of a game based on subscription fees is World of Warcraft (Activision-Blizzard) that once reached its peak at 12 million active players in Q3 2010, now it has around 7 million subscribers.
Some companies opted in for a tabula rasa and went from a subscription-fee based business model to a F2P model. We were able to observe this kind of behavior on a given number of Asian MMORPG’s, one of the most talking example is Aion. Aion got F2P in February 2012 and offers in parallel virtual goods that may be considered pay-to-win.
Other companies adopted less drastic measures and implemented only partially a free model like Star Wars: Old Republic (LucasArts/Electronic Arts) where the player has free access to the full story line, but once he reaches the end he is invited to pay in order to access additional end-game content.
The general idea of subscription fee based games is to offer new content periodically to counterbalance boredom. If there is no flow of new content people lose interest in the game and stop playing. Since the game has a subscription fee, they abort the payment and there is a high chance they will never come back due to the fees involved. Russian developers had the idea to create a World of Warcraft clone called Allods Online (Allods Team) based on a free-to-play model and monetized a lot of money until it became too strongly pay-to-win and they lost the playerpool.
Knowing that competition in the gaming industry gets harder and harder, companies focus more and more to offer games based on a free-to-play model. So we have on one hand companies making traditional games by focusing on how to entertain the player and on the other hand companies making F2P games that in addition focus on monetizing the player’s enjoyment by sometimes making the game like quicksand, once you enter it it is hard to get out.
Varieties of this model are numerous, beginning with social media platform F2P, passing by Asian games with the revenue model based on in-game shops and finishing of by games based on season passes.
3.1.1 Social media platform based free-to-play model
Social games are ones of the most thought through when it comes to game design. More precisely the level of detail that is given for developing mechanisms that make the player stay in the game and to convert him to spend money is very advanced. Most of social media games are based on so called offline progress mechanics (OPM) and a double currency model (DCM).
OPM is based on two techniques that are supposed to lure the player to come back to the game periodically, pay and invite friends. First of all by introducing the energy mechanics the player has a given amount of energy or lives and after he used them he needs to wait or pay in order to continue playing. The appointment mechanic is the second way to make the player come back periodically by making him wait until a construction process is done or if he invites his friends that accept to enter the game, the construction is done immediately.
DCM was defined at the same time as OPM by Fields & Cotton in 2012 and it works as the following, the game gives you two types of currency, one that is easy to obtain and another, more rare, that is hard to get or only by spending money. This second currency is exclusive and represents a given value to the customer that is superior to the first currency.
These mechanisms have proven their efficiency even if experienced people in the video game industry start to get a heavy feel of it there are more and more newcomers to try out some games casually.
In the graphics situated above we can see the nature of social games like Farmville. The spontaneity can be seen via easy game access, symbolic physicality via gifts, sociability via the fact that the player interacts with his friends, narrativity through messages and last but not least asynchronicity via freedom of when the player wants to play. The last anchor is very important, because until 2009 it was unsure if an asynchronous gameplay style would have rather positive or negative influence on the gamer’s play-experience.
3.2.2 Asian in-game boutique based free-to-play model
The leading free-to-play model adept in the Western Markets is with no doubt Aeria Games. This company owns more than 40 games and has a player pool of more than 40 million players. This company is a master in what comes to online in-game boutique. A huge variety of items and services is proposed to the player. Different systems are developed to make the consumer pay money.
In-game goods and services that boost the ARPU (average revenue per unit)
|Gear & enhancements|
|Costumes / vanity items|
|Gambling systems for all the above|
A good working but very frustrating and in my opinion offensive system that maximizes monetization is the gear enhancement system. The idea is to create a chance based system where you can gamble to change stats on an item, if it fails you item gets worse or even destroyed. In the interest of insuring that the item is not getting destroy, the company comes up with an anti-enhancement-failure consumable that it recommends to buy in the in-game shop. On the top of that the enhancement system is based on random stats so rerolling multiple times is required to obtain the stats the player needs.
This is only one example of many techniques that got invented that make an active player want to buy in-game items. We are getting to a point where enterprises start to understand that such invasive techniques are not always good, because the reputation of the game and the company itself develops a negative connotation. It is more preferably to create content that the consumer buy because they are free to buy it and they want to buy it without to feel like they have a disadvantage by not buying things in the in-game boutique.
Some developers did a good job and you can see it not only on the critics present in the web, but also by the results. The Lord of the Ring Online (Turbine), once transformed into F2P and added a Cash Shop, the profit tripled.
Like we can see on the illustration above, creating limited on time or quantity offers and other tactics can maximize revenue in an in-game shop. Also adapted advertising is important, it should not be too invasive, but always present when some good or service from the store might be useful.
3.2.3 Season pass based free-to-play model
Initially you can download the game for free and after some time the company offers an expansion pack, an add-on, new content. In order to be able to play it you have to pay. You can still continue to play the old content, but from a psychological point of view, if you like the game, you can’t miss on it. The idea behind this model is to show off a good game with polished graphics and good player’s experience. Once they reach to persuade the player by its promising lunch of the game, they offer additional content you have to pay.
A good example in order to illustrate this concept is Defiance (Trionworlds) that is a free-to-play game based on the TV-Series Defiance in which you could buy a season pass at start that gave you access to new content that was not available yet. The inconvenience for the player is that he doesn’t know when the content is coming out. The advantage for the society selling the game is that they get the money for content upfront.
All the work is to convince the player by showing him promising content or by referencing the game title with a TV-series. It is easier to sell a game that doesn’t even exist if it has to stick with the storyline of TV-series, a movie sage or ultimately a book.
After we saw the varieties of F2P business models, it would be interesting to see the key characteristics of free-to-play games on the side of understanding the difference to traditional games.
In order to satisfy the experience players receive by spending time on free-to-play games some key game design features have to be assured, otherwise the player will play a different game.
Here a non-exhaustive list of elements retaining high importance:
The idea behind this objective is to say that as easy it is to get someone to play your game, as easy it is to lose him, because he can just change the game to another F2P game since there was no monetary charge involved. So the question is to find a way how to keep a player once he started to play you game.
This contrasts with a player that has spent money, because he feels a bond with the game and invests at least some hours to be sure if he wants or not to continue playing it. He actually invested time and money to get it, that’s why one of the challenges is to provide immediate satisfaction and show him the possibilities of the game.
This is a key vector in which a lot of thought has to be invested. It is logical that the more someone play a game the more he finds himself involved in the game, he starts to like it, he becomes part of the community, etc. So the more time a player plays the more the chance he will spend money on it. That’s why it is unthinkable to not focus on the longevity of a game. The idea is to create brief but intense gaming experiences. The player is supposed to play short and often and for months.
As we can observe on the following graphic, the audience becomes more and more heterogenic, young and old, man and woman play all kinds of games.
With for example more and more woman playing video games the expectations change. Women in general prefer to play more softcore games where interpersonal relationship is involved, where man prefer violence, action and pure competition.
We can also distinguish between older players that are over 30 years old and have only little time to play. For them game sessions have to be short. Where younger people like to see their character evolve, get achievement to feel like they actually achieved something in their life.
This is another very important factor, people don’t like to lose time to make fill in forms, download content, register, rearrange keyboard before even starting the virtual adventure. That is why Facebook games are so popular. In order to illustrate my example we have the plug-in graphics engine called Unity 3D. Statistics show us that 40 percent of players didn’t finish downloading the engine, which results of them not trying out the game.
A very important feature in games is the tutorial at the beginning, no one wants to jump into a game and have no idea of what he or she is supposed to do.
Intuitive and easy to use interface is important, because if it seems too complicated a casual player might just give up and focus his attention on another game.
Play little, but often
Like already said before, a distinctive feature in F2P games is that they are designed in a manner to attract player to come back. This gives them companies that are making those games several advantages.
First of all it creates frustration, the player might give up and just spend money in order to play more without waiting
Second of all, if a player logs on every day, he will see advertising every day, what means a higher exposure.
Last but not least, F2P games are often based on repetitive tasks, by limiting the daily gameplay time, the players avoid to be bored.
Open loop principle
People like to accomplish achievements, close loops, it feels fulfilling. So like the social game consultant Tadhg Kelly thought, making an open loop makes people come back into the game. We can observe this in a lot of games, as example I present to you Backyard Monsters or Farmville, every day you accomplish tasks, create a bigger and stronger empire. The farther you advance in the game the stronger your enemies become and the game has no end. Even more talking examples are Mobster and Mafia Wars in which you have to buy infrastructure that makes you earn more money, but it attracts more villains and you have to defend yourself. By defending you send more money and so on.
Limiting in-game resources
The idea is to give the player a defined number of moves, lives, health, energy, etc. and motivate him to buy new lives.
Giving the player bonus experience or in-game currency if he logs on every day is a great way to make him finally play the game more.
Create special content for cooperative playing with friends or make things only doable if friends help. In that way the player himself is going to promote the game to his close connections and like we can see in the last report of ESA word of mouth has an important influence in the decision making.
From now on we know how to obtain and maintain a healthy player basis thanks to adaptation of the game to new trends and habits of players by focusing on a given number of key levers. The question we can ask ourselves now is what kind of exclusive service and goods players are looking forward to spend money on in a free-to-play game.
In this part our attention is going to be focused on specific cases of video games representing interesting mechanics inside the game itself. Some might involve in-game auction houses, others techniques allowing to counterbalance inflation rates and so on.
Virtual economy or also called synthetic economy is the term that defines a new type of economy existing within a virtual space. In our case the virtual space is the video game. Some games present advanced economic models in direct application inside it. A good amount of people consider economy in those micro spaces as nothing serious, because it is around video games. However, these models work and may even be very lucrative in form of real money. Depending of the economy inside the game and the situation, prices of certain goods may fluctuate. If an experienced player knows how real economy works, he or she can apply those principles inside the game and generate benefits. These virtual benefits can than later be exchanged against real money by selling it on the internet.
There are several more or less effective methods that allow game companies to generate money.
The most common and best working techniques according to eMarketer are the following (% of money generated thanks to this method):
- Item-purchasing (60%)
- Affiliate marketing (20%)
- Advertising (20%)
Then we also have revenues generated by:
- Restricted access
First of all we have item-purchasing. This is the primary method of monetization in free-to-play video games, it represents 50 to 90 percent of the revenue generated by companies.
We can define certain families of in-game items, beginning with cosmetic items like weapon-skins, character-skins (Pet Society), mini-pets, mounts, etc.
Then we have boosters, they are most commonly used to gain more in-game currency, experience or loot. Boosters make it possible to speed up time in-game (Edgeworld) so the player can advance faster if he or she doesn’t want to invest too much time.
The third category of items are convenience items, here we have a big variety of items that make the game easier to manage. For example we can find extra tabs for the stash (PathOfExile), faster travel, additional character places, instant respawn, no reparation, extra information about teammates and so on.
Add-ons to the main game can also be purchased, for example maps, quests, storylines (Dark Souls 2), heroes, etc. Another common category of in-game items that gained lately on popularity are collectible items. Facebook games and MMORPG’s often offer mini-pets, cards, costumes, buildings (Treasure Madness), special dyes or followers. The makers of Path of Exile also sell so called supporter packs that go up to 1.100 dollar. In my opinion it is not anymore a micro-transaction and one might ask how the taxation works on that.
Second of all, advertising plays an important role in monetization of F2P games. This method is working surprisingly very well, because players know that the developer of the game needs to earn money somehow. There is no negative connotation to advertising as long as it doesn’t interfere directly with the game experience.
The third pillar of revenue generating in F2P games is the affiliate marketing. The principle is simple, if a player goes on a partner’s site and registers or tries out the product, the developer of the original game gets a small amount of money.
After we saw the three main generators of money, we will see how another branch of monetization through freemium and restricted access works.
Dungeons & Dragons Online (Turbine) for instance is a free game, but the consumer can opt for a subscription in order to have access to other characters or quests. This system is hard to balance, on the one side the game can’t offer to easily access to items otherwise no person will be interested in a subscription. On the other hand, if the subscription offers a huge advantage in contrast to normal players, the game will be considered as pay-to-win. As for the restricted access model, the game Dofus (Ankama Studio) is a good example, the game is free, but exchange with other players and access to a certain number of dungeons is restricted. In order to have those privileges, access need to be bought. Here once again, the choice of what is accessible and what is restricted must be balanced, otherwise it could generate a lot of rage in the community.
If a game is for free, why should you send money on it? Well there are a number of desires that will be briefly presented in the following graphic:
- Level faster: instant completion of constriction or more experience gained while playing the game
- Access to new content: Propose a game where you can give it a try and if you like it pay so you can access endgame.
- Enhance the game experience: be able to have exclusive spells, use mounts that movie faster etc.
- Look better: it is possible to look better in-game, have better looking weapons, customize the look of you character and much more esthetic enhancers, this is the key lever in a micro-transaction based game (Path of Exile)
- Make gifts: if you would like to make a surprise to a friend that plays a game you can make him a surprise and buy something that he can use in-game
- Access exclusive features: customizing of game interface, automated managing tools (Ogame)
- Feed someone’s ego: customizing avatar’s on social based games or enabling the possibility to buy special “cool” looking units to attack your friends is for some people a way to show off in front of everyone
One of the most controverted experiments to try to limit illegal exchange of in-game goods, the Diablo 3 (Activision-Blizzard) Auction House was a big flop and put in danger one of the most anticipated games of this decade. In order to avoid a shady black market around the game that would allow players to exchange items they need against money, the Californian company decided to create an in-game real money auction house with commissions and control over what was being sold and by whom. With the release of the expansion pack Reaper of Souls, the auction house got closed for good.
One might ask: “What happened?”
Well the game relies on one main pillar, it is that makes it original and unique in his genre, the collection of items. As soon as people could buy the items they needed, the game become a pay-to-win adaptation with no more purpose. Eventually prices deflated and you could get a godly weapon for 3-5$, way better than anything you could expect to find on you own while playing the game. Not much long after release the auction house was filled with bots and clunky UI’s. The battle you had was not more against demons and zombies, but automated auction snipers.
As we can see on the illustration, the currency system in video games can be rather complex. In the case of Guild Wars 2 cash is part of the economic micro-system. It is possible to change real money against so called Gems. With Gems it is possible to buy exclusive Gems items, but also the main game currency called Coin. Coins can be spend in many different manners. Since Gold is getting generated by playing and by real money acquisition, there must be a gold sink mechanism. It consists on balancing the inflations of in-game money by its destruction. It can get consumed by the auction house, repair costs of armor and by a bit of gambling. Alternative currencies also exist, they mostly have a precise goal inside the game, for instance Dungeons Tokens are obtained by playing dungeons. These make it possible to buy exclusive armor and weapon skins.
WoW being the most popular MMORPG since 2004 has done some good changes in order to satisfy all the community. At the same time a lot of different services around this game got developed.
A player can pay a person that will power level his character to a certain level, prices move around 150€ and it takes 5 days.
This business is very lucrative in China. Even prison owners decided to make their prisoners work in front of the pc farming gold in World of Warcraft. It appears that there are more than 100.000 full-time gold farmers in China. When the game come out, it was possible to make 5,000-6,000rmb (470-570£) a day.
Other than that, WoW creators invented an interesting concept, the WoW Token. This special token can be bought with in-game currency. Its function is to add 30 days of game time to the player’s subscription. This makes players stay in the game and continue playing, the developer gains a lot of money by having an important player retention rate. Having several million players, it is possible to generate important benefits by selling only extensions.
It is possible to use game currencies to buy real money. The principle is simple, Second Life has a currency called SLL. This currency can be generated inside the game or it can also be bought on exchange platforms like VirWox. Once you have the SLL’s on VirWox you can exchange it against Bitcoins. Those Bitcoins can be send on a virtual wallet like on BTC-e, a digital currency trading platform. Once the money is on the virtual wallet, it is possible to exchange is against other currencies like Euro, Dollar, Litecoin, Dodgecoin and many more.
Introduced by Activision-Bizzard, Hearthstone is having more and more success during the last months. The game is a free-to-play game with free downloadable content (DLC) that comes out periodically. Payers can unlock the new content with in-game gold or pay money, but there is no need to. That’s what makes the system so interesting. It is also important to add that the downloadable content gives more advantages to players than just buying packs. Certain cards get unlocked when the player finishes the content so that’s why some consumers opt for buying the extension upfront.
In our days real economists get employed to control fluctuations inside a video-game. A good example is EvE Online (CCP Games), this game has a deep and complex economy system based on exchanges. Given players can be traders, but also take part of consortiums, corporations, alliances, etc. Financial institutions are present in the game (EBank collapsed in 2009), some of them make illegal transactions of virtual money against real money on the black market.
Some say: “It’s only a game”, but real money benefits can be generated only by playing a game, the economic system is based on real economy. So called virtual goods generate a lot of money, in 2012, Americans spend 2.9 billion dollars and the Asian market is even bigger. Some universities make studies on games to analyze behavior and predict how real economy could react on given experiments based on the results of in-game economics. Thant’s to different analyses, it was possible to determine how players play and what their behavior is in-game. This makes it possible to adapt the strategy to sell more items and services.
As described here, the game industry is a rich segment of the media branch. Multiple changes take place and companies adapt their behavior, and therefore their products, to favor consumer needs. As this market expands, the time spent in cyberspace grows more and more and it has become a common practice to live a part of one’s own life in a virtual world. Is it progress we should be proud off or should we worry about the imminent future of our children? It seems clear to me that virtual transactions and economy can save time and money for everyday consumers and can also be used to make experiments and analyze them to adapt them in real life.
If we put aside (valid) interrogations about ones social life if he or she spends too much time on any game, the analysis of the ever-growing economy of the video game industry shows us that any given economical system is not doomed to last forever. New systems shall always be created and will eventually change consumer’s habits!
As we can observe, the F2P market is getting saturated, a lot of games fail because they get copied. In order to stay competitive new themes, new refreshing scenarios must be offered. Creativity and innovation should find new niche audiences. Games like Free Realms (SOE) are showing the example, a F2P game on Sony’s console Playstation 3. The embedding of microtransactions in consoles can be considered as progress or at least a merging tendency of a new variation of the F2P model. It is clear that players will not pay for extra content if that content is considered to be part of the basic game itself. Games are no more stand-alone products, but games are services. We have to get used to it, shall it be the consumer or the developer. It is once again time to see how the balancing between the supply and demand will go out in the next months and years.
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- GameIndustry International, How to monetize Free-to-Play Games, http://www.gamesindustry.biz/articles/2012-08-25-how-to-monetize-of-free-to-play-games
- Dan “Shoe” Hsu, Why gamers hate free-to-play, and how developers can work around it (interview), http://venturebeat.com/2013/09/26/why-gamers-hate-free-to-play-and-how-developers-can-work-around-it-interview/
- Victor Garcia, Free-to-play: le “modèle Candy Crush” va-t-il s’imposer dans l’industrie du jeu vidéo ?, http://www.lexpress.fr/culture/jeux-video/free-to-play-le-modele-candy-crush-va-t-il-s-imposer-dans-l-industrie-du-jeux-video_1655781.html
Business models for digital goods: video games (free-to-play games), http://www.ipdigit.eu/2015/03/business-models-for-digital-goods-video-games-free-to-play-games/
 The Numbers, http://www.riotgames.com/our-games
 Hearthstone Hits 20 Million Players,, Shuffles Toward Mobile, http://www.forbes.com/sites/erikkain/2014/09/16/hearthstone-hits-20-million-players-shuffles-toward-mobile/
 Ruri Lee, Analysis of Activision-Blizzard and Electronic Arts p.20, June 2013,
 Number of World of Warcraft Players from 1st quarter 2005 to 1st quarter 2015, http://www.statista.com/statistics/276601/number-of-world-of-warcraft-subscribers-by-quarter/
 Janne Paavilainen, Games sin Social Media, http://www.oamk.fi/cdn/fileuploads/games_in_social_media.pdf
 Janne Paavilainen, Social Network Games: Players’ Perspectives, http://people.uta.fi/~kljuham/2013-paavilainen_et_al-social_network_games_players_perspective.pdf
 Janne Paavilainen, Asynchronous gameplay in pervasive multiplayer mobile games, http://dl.acm.org/citation.cfm?id=1520642
 Tom Nicholas, Monetization Lessions from Asian F2P Games, http://gdcvault.com/play/1019776/Monetization-Lessons-from-Asian-Free
 Tom Nicholas, Monetization Lessions from Asian F2P Games, http://gdcvault.com/play/1019776/Monetization-Lessons-from-Asian-Free
 The Design of Free-To-Play Games, http://www.gamasutra.com/view/feature/6552/the_design_of_freetoplay_games_.php
 Thoughts of browser plugin penetration, http://blogs.unity3d.com/2008/03/31/thoughts-on-browser-plugin-penetration/
 Edward Castronova, On Virtual Economies, http://www.gamestudies.org/0302/castronova/
 Paul Tassi, “Diablo 3” Finally Exorcises Its Demon, The Auction House, http://www.forbes.com/sites/insertcoin/2014/03/18/diablo-3-finally-exorcises-its-demon-the-auction-house/
 Paul Tassi, “Diablo 3” Finally Exorcises Its Demon, The Auction House, http://www.forbes.com/sites/insertcoin/2014/03/18/diablo-3-finally-exorcises-its-demon-the-auction-house/
 Biox Eirh, [GUIDE] Converting your currencies to Gold, http://www.reddit.com/r/Guildwars2/comments/1ocogi/guide_converting_your_currencies_to_gold/
 Power Leveling in WoW, http://www.mmosale-fr.com/wow-powerleveling-honneur-reputation-p-565.html?zenid=pohisc01lnontjej9nolob0so5
 Danny Vincent, China used prisoners in lucrative internet gaming work, http://www.theguardian.com/world/2011/may/25/china-prisoners-internet-gaming-scam
 WoW Token Info, https://wowtoken.info/
 BTC-e, https://en.wikipedia.org/wiki/BTC-e
 Paul Tassi, Hearthstone’s “Curse of Naxxramas” is an expansion of the concept of DLC itself, http://www.forbes.com/sites/insertcoin/2014/07/22/hearthstones-curse-of-naxxramas-is-an-expansion-of-the-concept-of-dlc-itself/
 Brad Plumer, The economics of video games, http://www.washingtonpost.com/blogs/wonkblog/wp/2012/09/28/the-economics-of-video-games/
 Cf. above
 Eva-Maria Scholz, Business models for digital foods: video games (free-to-play games), http://www.ipdigit.eu/2015/03/business-models-for-digital-goods-video-games-free-to-play-games/