TRU offered $25 credit when you bought this the week it came out. I had it the first time I had a Wii, and I recently got my wii back...this is one of two games I still want to "re-get", the other being Super Paper Mario...but man the first-party titles are expensive.
I also don't buy the $10 off another purchase as a savings on THIS purchase. You still have to buy something else.
That said, I do already have $10 credit from a previous purchase, so if it were $30, I'd probably bite, but $40 is still too much.