I mean, just make it 30%, or whatever, of stuff that uses their in-built app store payment. If you don't want to use their payment infra, you don't pay and you make whatever arrangements with the user both parties agree to. It forces them to justify their cut other as more than just rent-seeking. Netflix doesn't need any help getting a CC number. Or delivering apps, frankly. Apple inserts themselves as a middleman in that capacity for their benefit and theirs alone.