Apple also benefitted from third-party developers writing software for its platform. Remember the "there's an app for that" ads?
I think developers deserve to be treated fairly by Apple, not exploited four different ways. Because to develop for Apple you need:
1. Buy Apple hardware, because Apple doesn't provide cross-platform development tools (unlike Android or even Microsoft).
2. Pay $100 a year just to be able to publish the software.
3. Pay 30% of the app income to Apple (this changed only recently).
4. Have to endure odious restrictions imposed only because Apple wants to keep control of its platform.