I was gonna say dirt cheap but I guess prices have increased a bit since the last time I looked. If the bare console is enough, it should still not be more expensive than 20, plus another 20 for the Game Boy player if you don't have one yet. That is without shipping though.So how much would a PAL NGC with some way of using GBI run me these days? I've been wanting to play gamecube and gameboy games recently and realized I don't have a great solution for recording either at the moment, though I do have a wii.
Edit: You'd still be missing a way to use GBI. I hope someone else can help out here because I'm not too knowledgable on this subject.