No, of course not, but Apple is essentially triple dipping in this regard. Lets break down the costs.
1. A $100 annual developer subscription. It could be argued that this goes towards SDK development, developer tooling, and App Store publishing systems.
2. The 30% fee when selling your app. Similarly, it could be argued that this fee covers application hosting and distribution, as well as advertising, and I guess as a "general fee" for selling your app through the App Store.
3. 30% on all in-app purchases. Given that Apple has no part to play in this (the application was already advertised and distributed, no additional hosting fees as developers are responsible for implementing/unlocking whatever happens once the purchase goes through, etc), what does this cover other than payment processing, which is normally charged at 2.5%~?
Would you consider providing a large number of paying customers "of little value?"