this answer is not tryin to be smart but the real answer is because its a nintendo game they know they got the best games on the wii so they wont lower the prices for a while.as far as where to get it cheaper...wish i knew because i ben waiting for it to go down in price. hopefuly since the wii u is out it will go down in price.
Mario has tremendous selling power. "Super Mario Galaxy" did not go down in price at all until the "Nintendo Select" series came out, despite being several years old. All the main Mario games hold their price point for years after initial release.
It has to do with zero economic skills. People who have no grasp of economics try to profit from things that are rare and believe that means they have a high value. The law of demand always proves that one must lower price in order to sell more than one item. Value only exists when a sale actually happens. This is the definition of value.
To the seller: What does your demand schedule look like? Is it low? Try matching the low demand with a low price so you can clear your shelves! Unless you're happy selling one copy a year...
I'll make it easier for you:
Target, Toys-R-Us, Best Buy, Gamestop, Kmart - all firms that follow economic laws and sell tons of copies instead of one every blue moon. Their price beats yours by $10 - new as well, same box, same everything, no shipping, available today.
Lately, I've seen some online vendors selling it for $29.99. I don't expect it to go any lower with the WiiU and DS consoles being Nintendo's main focus. The original Wii is now a thing of the past. I'm afraid that "Super Mario Galaxy 2" prices will go nowhere but up very soon. Buy it now, and don't risk trying to find it when it's rare.