I don’t know where this idea that 30% is an unreasonable monopoly-sustained fee comes from. Stripe’s fee is 2.9% plus 0.30, so it would be way more than 3% on small purchases, which I assume are a lot of App Store transactions. Steams is 30% even though there’s compition (Discord tried to run a store with a 90/10 split and shut it down very quickly). Google Play is the same as Apple’s, and they allow other payment processors (for non-games). On the other hand, Audible has no competition, and they have a 75% fee (as in they keep 75%).

Most App developers aren’t even paying 30%, they’re paying the lower 15%.