Thanks for the reply Captain Falcon...
I get what you mean. However, Nintendo did a pretty poor job of advertising. I believe that if Nintendo pushed this game via ads in store, TV, Newspapers etc.. it would have been a sleeper hit imo.
On the topic of sales, I tried looking up any information for sales figures. I looked up VGCharts but I believe that they hold sales info for the first 10 weeks.
I reckon SP2 would be reaching the 1 million milestone (that's if its not surpassed it?).
Additionally, the 'SP2 team' is far smaller than team's for well known franchises so I'd hazard a guess and suggest that they must have made a healthy profit (in comparison to the amount invested into producing and publishing the game)?