Because Nintendo and Sony have no presence here and have to do all their distribution through dealers who want a bigger cut, MS exports their consoles themselves to Mexico, so they handle shipping, exports, sales, etc, there's a reason why tech support is quick as hell to repair a console (sent mine twice, once for a damage, the second time because they sent me a dead laser 360

) and they both took like a week or four days.
And yeah, I live really close to the border (Texas is about four hours or even less from here), so many people from here prefer to buy a PS3 or a Wii consoles in the US rather than here, with the taxes and the price of the 360, it's about the same to buy it here.
Me too, I need a new Gamecube that can read Wii games.
Oh, and Twilight Princess is $90 here. Compared to Uncharted 2 $30 or Gears 2 for $25, you can see what I'm talking about.
