First, my day rate as a professional full-time iOS dev is higher than what he paid for the entire project. Granted, I've been writing software for almost 20 years now, the last six strictly Cocoa and iOS, and I live in NYC. But even then, all I can tell him is that he got what he paid for.
Second, if a client is going to withhold final payment based on Apple acceptance, there is no way I would work for them. Specially for some dumb app like this.
But the part that really irks me is the last bit about "doing it yourself next time". Good luck with that. I would love to be around the moment you have the epiphany about how much you got for how little you spent and what an asshole you are about whining about it.