Earlier quoted context omitted.
As described in the ruling, Apple hired a consulting group to estimate how much value developers get from the iphone platform, which found that (1) Apple’s platform technology is worth up to 30% of a developer’s revenue. (2) Apple’s developer tools and services are worth approximately 3%–16%. (3) Apple’s distribution services are worth approximately 4%–14%. (4) Apple’s discovery services are worth approximately 5%–14…
It made me laugh, if you pretend to be worth 30% of revenue (an insane markup), you better really invest in those developer tools to show it off because the sad state of xcode really isn't showing that. I don't know where this money is going but certainly not in the developer tooling because it's absolutely terrible
Back in 2008, if you were an indie dev then their 30% ask was more than reasonable because the cost-of-doing-business on other platforms (like Windows Mobile) was much higher due to the lack of any central App Store; for example, you'd often need to partner with a company like Digital River, and pay more for marketing/advertising and overcome the significant friction involved in convincing punters to register/buy from your website, download the app *.cab files to their PC, install the app onto your device, and hope no-one uploads a copy to a filesharing network because this was before the days when an OS itself would employ DRM to enforce a license for third-party software.
...then one day Apple comes along and says: "We can manage all of that for you, for far less than what you'd pay for e-commerce and digital distribution, and our customers have lots of disposable income".
Ostensibly, competition should have come from the Android and (lol) Windows App Stores: "surely if Android's Play Store offers devs better rates then devs will simply not target iOS anymore and Apple will reduce their % to stay competitive" - but Apple's secret-sauce of a markedly more affluent customer base with already saved credit-card details meant that Android apps leant more on ad-supported apps while more iOS apps could charge an up-front amount, not have ads, and result in iOS devs still making far more money on Apple's platform.
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There exists an argument that Apple should not be forced to open-up the iOS platform because Apple is selling a closed platform on the merits of it being a closed platform, and Apple's customers want a closed platform (even if they don't realize it) because having a closed platform looks like the only way to enforce a minimum standard of quality and to keep malware out precisely because normal-human-users (i.e. our collective mothers) will install malware because the installation instructions for "Facebook_Gold_App1_100%_Real_honest.app" tell them to disable system protections.