It seems like the Gamecube adaptor for Super Smash Bros. for Wii U might end up a collector's item. Most places has run out of them already, and My Nintendo News reports that Nintendo don't plan to make any more at the moment. We've contacted Nintendo Europe for a comment on the matter.
As it is right now, prices for the adapters on Amazon starts at $100. That's more than the game plus adapter combined new when the bundle was first released. So if you've got yours pre-ordered ahead of the European launch this week, count yourself lucky.