Either an effect of the pot simmering over with enthusiasm for game collecting, or the fact that GC was far more obscure than PS2 or Xbox. Maybe a bit of both. GC proves to be almost as hard to find in the wild as Dreamcast. I'm shocked that Xbox remains as cheap and unloved as it still is. GC is going up, PS2 is on a steady rise, but I think Xbox is about the same as it was 5 years ago.
Earlier this year I checked everything on VGPC, the only consoles that hadn't seen a large increased average since 2009 was basically everything Sega (- SMS), and XBox. PS1 had actually gone down. Everything else has gone way up. SNES tripled I think.
Nowadays it doesn't surprise me to hear about
anything becoming valuable. Especially if it's a game I never bothered to pick up.
There are in fact valuable Wii games already, standard release ones. Wii prices are set to go way up in the near future, I'm almost certain.