People who already had the Wii version of Dragon Quest X, they got 50% discount on the WiiU version if they bought it from the eShop. I think the expansion sales numbers shows that several of people used this eShop opportunity.
Why are the other 5k buying it without Mario, isn't Mario / Wii Party basically free in the bundle? Of course, I would buy a Wii U without it if the difference was even 1, because I want my games as "real" games, and not just downloads, but in that regard I'm probably "special" ^^.
You know if Nintendo had a 2nd game ready around this time like Mario Kart 8, the momentum going into 2014 could've resembled the 3DS, along with DK on February it could've meant a nice start of a turnaround.