What do you mean by economic incentive?
That Apple based apps are harder to copy/pirate or that that because Apple apps are checked by Apple people are more willing to spend money on them due to better transaction security?
Dosen't much matter to me, the app I'm intending to make (when I get my new computer) is going to be free to download and involves accessing a database of content that I control so people can steal my app all they damn well like. What concerns me is that Apple won't let me set it up that way, that I'll have to enter into some kind of agreement regarding the nature of the content or they'll want to "host" (control) my database as they see fit.