The average App Store customer buys less than $20 worth of apps last time I saw numbers quoted. 30% of $20 is $6. Apple is a hardware manufacturer that sells $X00 phones at one of the highest markups in the industry and also gets a kickback from AT&T for every customer they bring to monthly billing.

Apples' incentives are almost totally non-related to developers' incentives: their primary interest in apps is to move more hardware and contracts.