If the wii u had sold well Nintendo would have made amazing profits as the console is manufactured from such low cost components. It's likely even cheaper to manufacture than a hard drive equipped ps3 or 360. It's an incredibly cheap design.
However it failed to sell in the expected volume Nintendo had hoped for so Nintendo built up a lot of unsold inventory which I think they wrote off financially.
It's hugely likely that the wii u has been very unprofitable and has been subsidised by the 3DS console and cartridge sales. 3DS is quite mature now and manufacturing costs would have reduced and R&D costs paid back.
Of course I don't have the full figures as Nintendo don't release them in that detail but I can't see 8 million console sales being enough to be profitable.
