No you are incorrect: If you want to sell an app for iOS, it needs to go through the App Store, and it needs to go through Apple's payment processor, be hosted by them etc, and Apple will take 30%.
There are 'work arounds' that involve being enrolled in the Enterprise Developer Program, but you're still at Apple's mercy. If they believe you're not sticking 'to the spirit of the program' (e.g. using it just to get around the App Store) they'll terminate.
To be fair, Apple handles a lot for that 30%. Accounting/Tax records, payment, bandwidth and storage etc.
They could probably afford to take less, but they do take care of a fare bit of hassle from app distribution and selling.