Don't forget, Apple provided the App Store (you know, like Wal-Wart). This is where the consumers come to shop for stuff. Oh, also add in the small ingredient of the actual CONSUMER. Apple created them too. Without the hardware and it's ability to use apps, the millions who purchased it wouldn't need a store or developer to begin with.
AT&T only provides the pipeline if actually download apps on the phone. Consumer's can use their ISP via iTunes. Also, don't forget the consumers pay for the data from AT&T, NOT to Apple. So in my estimation, AT&T is getting their fair share. As far as the developers: they can charge whatever they want (free or a $.99 minimum). Apple doesn't regulate their prices. If the developer does a good enough job, they could sell their apps for $50, 60, 70...whatever. The market drives the best price, not Apple.