Instead of Apple offering an In-App purchase I have imagined a new system to earn and save money. To sell premium service in my app, the client should pay a certain amount of bitcoin i.e. with his bitcoin wallet app like Copay. In my app that would be a view called Contribution, where the user could see all his transfer sent to my personal bitcoin account. The view would have a funny title: "There is no free beer. Support developer with X bitcoin. (appr. 1$)" In bitcoin, all the historical transfers are available for download, that is what the app would use to check whether he paid or not. At the bottom I will put a link, a button to a Wikipedia site and a youtube site, how can users use a bitcoin wallet.
App Store Review Guideline 11.13 says: Apps that link to external mechanisms for purchases or subscriptions to be used in the App, such as a "buy" button that goes to a website to purchase a digital book, will be rejected
In my app user could get 50 pieces of service for free, and from 50 each 50 would cost a certain amount of bitcoin. When the user reaches the next 50 limits, app will automatically navigate to the Contribution view in the app. And user will not able to continue until I get my bitcoin. He is not linked to a payment system in the sense he has to close my app, manually download/open i.e. Copay and send me the money. No Buy button will appear. But it will be obligatory to pay.
Do you think Apple will accept my so-called 'support the developer' business model?