Do you like trophies? In the new venture of Sony in USA the trophies can yield credit points in PSN. That is, achievements in exchange for MONEY $$$. The trophies yield:

100 silver trophies - 100 points
25 gold trophies - 250 points
10 platinum trophies - 1,000 points

1,000 points will give you $ 10 credit. Little, but those who are not in a hurry can accumulate to buy the games.