It's because it's a limited set with a guide and bunch of other stuff packed in.
Most think once that first print runs out they'll probably put out a $40 game only version. Who knows if that will be in the promo period or not.
I think I'm going to pass as I just don't think I'd like SMT much. I'd like to get Fire Emblem eventually though. So maybe I'll take the plunge if I can get a hold of an SMT code for $10 or so for someone that doesn't need it.
It's 49.99 on the eShop.