Of course it's a system seller.
You play the game then you go to your nearest gamestop to sell your 3DS.
I just almost choked on my breakfast, lol. Thanks for that. You get a +1!
But yeah, MoF is DEFINITELY not worth getting a 3DS for. I enjoyed some parts of MoF. It wasn't a bad game, but it wasn't really good either. I at least was able to get through MoF unlike LoS. IMO MoF was better than LoS, but MoF was okay at best.
There are other great games on the 3DS that are out (Fire Emblem Awakening, Kingdom Hearts) or are coming out soon like Pokemon X/Y and Project X Zone though.