Earlier quoted context omitted.
The kind of ecosystem/business model that Apple has created is so fundamentally different from everything else that real world analogies just don't work. We should avoid using them in this debate.
It's more like, if you buy a Ford car, does Taco Bell owe 30% to Ford when you use their drive through? Or can Ford forbid Taco Bell from operating drive through stores of their own, and require Ford owners to go through Ford's own all purpose drive through stores?
If you get a job through a phone interview, do you owe Apple 30% of your salary? No.
Using your phone's services doesn't cause Apple to get a cut of anything that happens while you do so. Selling apps THROUGH ITS OWN STORE does.