We’ll, that’s where market forces push back on you. If you abuse your position then people (developers willing to work on your platform) walk. There’s a threshold, and I don’t know what it is, but Apples platform and it’s customers are currently worth the 15/30%.

I suspect that the number of developers at 80% would fall off a cliff. But that would be Apples decision to make. They set it at 30% and there are apparently plenty of developers who are willing to pay that rather than not develop for the platform.