This will keep happening as long as people keep agreeing to Apple's terms and building on their platform. I wouldn't touch Apple's platform with a 10 foot pole. Nothing here is new. It's getting harder to sympathise with developers who keep doing it.
I'll give you the counterpoint. I'm very happy to spend money on apps and services that I like. However, I'm only going to do it through Apple's platform, for a variety of reasons. If you don't want to build on Apple's platform, that's completely fine. I won't be a customer. And maybe that will change the system, I really don't know.
* Pay with Apple Pay ($13.00)
* Pay with Stripe ($10.50)
If their value-add is as strong as you say then surely they'd still make plenty of money. If not, well maybe they need to start adding more value or dropping their prices, just like anyone in a competitive market.