Is it still 30% when the app is having a marketplace where users are selling digital stuff to each other? I can not find anything about that in the guidelines. My use case is users that produces tutorials to sell to other users.
You can use whatever payment processor you want, but if you ship it on the App Store with in-app purchases, then Apple will demand a cut. This happened to a few dating apps in the Netherlands that implimented a similar workaround but still got invoiced for 30% of their IAPs.
