15 cents/day.
Actually, that was a joke, but I don't know how far off it is. So far this gen, I've bought 9 games, over 9 and a half month. That is roughly 290 days. The games cost 70 dollars average (That's Norway alright) so 2.3 dollars/day.
That's more than I thought...
http://www.vgchartz.com/games/userreviewdisp.php?id=261
That is VGChartz LONGEST review. And it's NOT Cute Kitten DS