Or for companies that don't pay via their payment system, couldn't they increase the annual dev fees to compensate, or tell those people they cant use their APIs if they are not going to pay from them or other tactics. If the rate is too high that's one thing, but assume companies don't expect to continue to get any marketing or resources from apple if they aren't paying for them in one way or another.
Apple is illegally restricting customer choice while not being monopolistic seems pretty balanced take on the whole issue.
Apple will of course appeal, however this is going to be massive for iOS store revenue.
They will be forced to drop rates or stand to loose a lot of developers from their payment system