When you want to buy a game for the Vita, you might as well as buy the PSN version of it. By just pressing a few buttons or by preforming a few taps on the screen, you can get the games, but cheaper. 10% savings to the exact.
Now everyone knows how to see how much you save on an item, right? Just multiply the price by ".1". That should give you your savings. Then you subtract that from the price of the game/dlc/etc., and your set. You have just saved that amount of money.