[alanstorm]

It's probably a part of a longer term pricing strategy. It's hard to start charging "real" money (even $40/$50) for an application you were formerly giving away for free. People feel like you've taken something away. By charging a micro-payment disposable price of $5 (Happy Meal, Latte, etc.) they deflect a lot of that criticism and avoid some of the negative publicity. Over the next 10 years they can slowly raise the price, each time keeping is reasonable.

Apple's leveraging the work they put into building the App Store infrastructure (and business deals with credit card companies) to do something a lot of other companies couldn't (make something that was free cost something again without too much fallout).