1. A development platform that includes the toolchains and emulators for all the variations of the Apple hardware/OS environments (including the ability to distribute test versions to a restricted audience)
2. A secure platform for taking payments, including all chargeback risk, local consumer taxation requirements (VAT etc) worldwide.
3. A secure platform for in-app purchases, subscriptions, DRM on content (leave aside the arguments for/against)
4. Mechanisms for secure distribution to employee BYOD of employer specific applications, including capabilities to remove them from departing employees
5. A marketplace with search and discovery (however imperfect) that also provides for customer reviews, screenshots etc
Currently all of that (barring the MDM of point 4) costs a developer:
* $100/year
* 30% of purchase/subscription/in-app revenue