They don't allow it exactly because they have to pay the 30% on top, the same with Kindle books, etc. that's exactly why it's relevant in this discussion, mate... Not sure how to be clearer, I've been playing around with your analogies and get just a brick wall in return, exhausting.

The whole argument is that they didn’t have a choice but to pay the fee when they in fact chose not to go through in app purchasing. They were not forced to pay Apple to be on iOS