"a cut of that" is doing a heck of a lot of work here to handwave the amount they're asking for.

A "cut" in this case means such a high percentage of the transaction that if Patreon didn't pass the extra cost on to consumers/creators, they would make negative dollars on each iOS subscription. That really genuinely does not strike you as odd at all?

It doesn't strike you as weird or maybe like a possibly negative market effect that Patreon as a platform should be more profitable for Apple than it is for Patreon? I think most people would say that's a signal that something might be going wrong.