Apple should not be entitled to any transaction that happens on the phone. They don't get a cut of money I move through my banks app. Anything I buy on the Amazon app. Do they get 30% of my water bill I pay? Again if something is being bought through the app store, like a game, an app, etc sure. But if your app is about a service that exists completely beyond apple, they should get nothing. Imagine comcast asking for 30% because it happened between your internet provider and an online store.