Supply-demand.
Maybe Sony wouldn't have to slash their software prices like that if their characters were as popular as Mario or Pokemon or DK or Zelda or whatever.
I get the feeling sales of games like LBP and Uncharted are highly inflated because Sony price crashes them quickly and/or bundles them with everything they can think of (even Dual Shock controllers).
LittleBigPlanet is a solid game with some interesting ideas, but when it comes to core platforming and level design, I'll take Mario every day of the week and twice on Sundays.