Then charge people for it. Apple has an annual developer registration fee, they should cover their platform costs using that instead of an arbitrary surcharge. If you want us counting our blessings, Apple also generously "gives away" access to a browser and phone app that don't see the need for all-encompassing payment processing. Those aren't giveaways though, those are basic features that have existed since before the App Store was an app. Apple's insistence on conflating their value is a textbook case of bundling.
Apple can be justified in charging whatever they want for their App Store if comparable services have a chance to compete. Nobody is prevented from sticking with OEM defaults if they choose.