OK, which games are a flop at 2-3 million? A new GTA selling 2-3 million would be certainlya flop, but that is the outlier. 2-3 million for something new, something that needs crafting skills (which isn't that common among gamers), something pretty expensive as it contains physical stuff - this is not bad.
I think nintendo invested a lot into this project and looking for a kinect like hit.
I doubt it. It probably had a small core team of about 10-20 people for one or two years, prototyping ideas and a big push with more personnel at the end to create a polished product. I think development was cheaper than for the new Kirby or Yoshi.
That's the point here: ideas are pretty cheap, if you have the right ideas. Development of assets like models and textures takes a lot of manual work.