The world\u2019s biggest app stores are facing increasing pushback by developers over the high costs they charge for connecting their games with users - and new gaming platforms are looking to swoop in. Tallinn-based Ultra will take 15 percent from sales it generates through its digital store, in a bid to challenge companies such as Alphabet Inc.\u2019s Google, Apple Inc., and Steam, the industry-leading platform owned by Valve Inc., which takes a 30 percent cut. The launch, planned for PCs as soon as November, comes amid rising push-back from game-makers and publishers against platforms that distribute games. Epic Games Inc., which created the hit game Fortnite, recently decided it didn\u2019t need Google\u2019s app store - which takes a 30 percent cut of sales, including in-app payments. Epic chose to distribute the game itself and keep 100 percent of the money it generates, though it still offers the game through Apple\u2019s app store, which also takes a similar cut. "There\u2019s no reason why such a big fee should be taken," Nicolas Gilot, co-Chief Executive Officer of Ultra, said in an interview. "The business model is totally viable without that." Global revenue for mobile, PC and console games is increasingly lucrative, expected to reach a combined $137.9 billion this year according to data compiled by market research firm Newzoo, increasing to $180.1 billion by 2021. Once dominated by brick-and-mortar stores, the industry is now led by online platforms that allow gamers to download from thousands of titles. Steam - launched almost exactly 15 years ago - generates about $4.3 billion in revenue, not including in-app payments or additional content, according to data compiled by independent monitoring tool Steam Spy. Game studios have long been competing with Steam. In 2011 Electronic Arts Inc. introduced its Origin platform and made it a required install in order to play many of its biggest new PC releases. Microsoft Corp. lets customers access some of its first-party titles early if they purchase from the Microsoft Store, including its next Forza Horizon release. Ultra is among a clutch of startups hoping to win market share by cutting costs and using new technology. Founded in 2017 and staffed by former gaming executives, Ultra plans to use blockchain technology to process payments and offer tokens to gamers who use its platform. Ultra\u2019s board includes Ritche Corpus of U.S. graphics card maker Advanced Micro Devices Inc., and Allen Foo, a veteran of both Microsoft and video-game development software company Unity Technologies. Ultra plans to initially offer between 150 and 200 games. The company is in the process of raising funds and has already collected about $10 million from private investors, according to a person familiar with the matter who did not want to be named discussing confidential matters. Spain-based Robot Cache is following a similar business model, using blockchain to track the sale of second hand games, offering both game studios and consumers a cut of the sales while taking a 5 percent transaction fee. Some question the ability of new entrants to reach a wide enough fan base. Green Man Gaming, the British online retailer, sells digital keys to games that customers can redeem on a number of platforms, including Steam and Origin. The game is then added to a user\u2019s account. Green Man takes about a 30 percent cut on each sale, while Steam makes money on in-game purchases. But the London-based company\u2019s CEO, Paul Sulyok, said the benefits of selling through a large international retailer are worth the cost. "We sell games in 195 different countries, 16 currencies, and support north of 80 different payments systems," Sulyok said, "and the cost of getting people\u2019s awareness of a product is significantly higher when you don\u2019t have a standard store." Google and Apple argue similarly, and say their stores offer developers access to users in more than 150 countries, technical support, and in some cases detailed user insights. Part of Ultra\u2019s business-model still mirrors its larger rivals, and may suffer from pushback of its own. Studios often roll out downloadable content to existing titles to keep consumers hooked. Google and Apple, as well as Ultra, take a cut of any of these add-ons purchased on their platforms. Frank Sagnier, chief executive officer of video-game developer Codemasters, said this ability for retailers to keep taking a slice of every transaction made within a game is a larger concern than the specific cut taken on an up-front sale. "If you sell a game during its launch period, there\u2019s a cost to doing that, so maybe 30 percent is justified," he said. "But once you bought my game start downloading content going forward, that\u2019s my customer. I think that\u2019s where the big distributors may find there could be some pressure."