Why should developers also pay for this, when end users already do? Apple is double dipping like a world-class monopolist (see: ISPs who charge both peers and customers).
Apple provides value to both end-users and developers. It does not seem unreasonable to charge them both. And if Apple did not charge developers, that would suggest they’d have to raise prices on end-users to make up the difference, which does not seem fair to the users.
To Apple developers are disposable, if you don’t want to make software in their garden someone else will clone your app there. They seem themselves as the ones providing value to you.
It won’t be long till they make more changes to make sure they get that value out of you on the desktop too.