You can trivially find countless counter examples where prices are higher only on the app store like netflix[1], spotify, etc.. subscriptions. They don't make their web & Android users pay more just to cover for iOS users, why would they? That makes no sense. So of course the price would drop if they were allowed to steer as they already sell it at the lower price on the website, they just aren't being allowed to tell iOS users that.
And that is what Apple is getting hit for here. Not the 30% fee, but the rules forbidding developers from telling the user about alternative sign ups or purchasing locations.
1: well before Apple cut a special deal for Netflix anyway
A mega corporation like Apple is much less likely to do this than a smaller company, though. Apple's quarterly dividend is literally the company communicating that they make so much money they can't think of anything better to do with it than just giving it away to the investors.
As long as the demand curve is downward sloping, there will be some pass through of Apple's cut to customers, though the fraction that is passed through will depend on price elasticity.
If you've got 10 overworked employees and you suddenly make 10-30% more money, you can hire another one or two people and the business runs better.
Isn't that great for me as a customer, though?
And I wouldn't exactly call 30% + x an extremely thin margin!