30% is a bargain. In physical retail we'd pay 50% pretty consistently. We were also at the mercy of the retailer to send things back to us if they didn't sell, without paying. So they would buy 20,000 units, sell 5,000, and a few months later send us back the remainder and call it even.
If we wanted promotion in their stores, circulars, or websites we had to pay for the privilege.
Considering Apple puts you in the pocket of hundreds of millions of people, puts you a password or fingerprint away from their credit card, and provides the opportunity for massive exposure in their store, it feels like a super fair deal.
I'm more troubled by the fact that they essentially have driven the price of discrete software to zero, but fortunately there are more and more ways to monetize via SaaS, IAP, Hardware, etc.