Would they also be unhappy if they knew the markup for every store? The markup for soda and drinks in a restaurant? Is there anyone who doesn’t know that retailers markup goods?
There's no developer on the planet that would agree to that deal if Apple couldn't use the customers from their phone business as leverage to extort developers on the software distribution side of things.
It's more like a bouncer at a club getting 15-30% of ALL revenue because they control the door.
Why do developers overwhelmingly give Google 30% of their revenue when Android users can sideload?
Should we also complain about the much larger margins that Amazon charges independent authors for Kindle? The amount Google charges for ads?
There are cases where 30% of revenue makes sense. For cheap, purchased apps it's a good deal because the cost of running that infrastructure is comparatively high. However, once you hit a certain volume of sales or move into subscriptions, the value of the services being provided by Google and Apple don't make sense and it would be better to run your own infrastructure.
Seeing what Epic was willing to do to get out of the Play store is a really good indicator of how bad of a deal it is at scale.
And I thought traditional retailers chose their own markup, didn't they?
https://www.cnet.com/news/just-as-critics-feared-fortnite-fo...
Edit:
Most retailers do choose their own markup. Ironically, Apple got sued for working with book publishers where the book publishers set the price and Apple chose the markup.
However, the book publishers wanted this arrangement because Amazon was selling ebooks at a loss devaluing the hardcover and paperback books.