Again, Wii you are much more prone to finding good stuff cheap. Gamecube library seems to have SNES tier prices these days, and it makes me grateful I already had some games before they started to shoot up, as well as having patience for local store screw ups ($10 Fire Emblem some years back).
What's really shocking is that fucking Melee, one of the bestselling Gamecube games, is a good $60+ these days, but considering how Dragon Ball Z: BT3 for the PS2 is in a similar situation locally, I speculate it's tournament players driving that particular price through the roof with heightened demand.
To be honest, I don't go looking online much for Gamecube games, because how prone people are to scalp for it. Locally I can at least stand to find occasional cheap worthwhile stuff, but it's been few and far between lately.
The PS3 is indeed rather cheap to pick games up for, though some games do hold their prices better than others. Where I live, stuff like Catherine, Tales of Graces f, and Dragon's Crown are all a good $30 or so right now, and some of the newer releases (LoH: ToCS I & II, Odin Sphere Leifthrasir, Tales of Zestiria) are probably still rather high, but admittedly I don't see copies of those around much where I live, Zestiria aside (averages $30 at Fucking Gamestop); probably not a lot of people that have bought some of those over the PS4 and/or Vita versions where applicable compared to the PS3.
I'd also recommend modding your Wii anyhow, as there's some good stuff you can do with it; look into Letterbomb. And if you're lucky enough to have an older model, you can even install bootmii as boot2 and have bricking reversion if anything happens.
Well, going off local prices where I am, it's about $12-18, so I'd say you ranged from average higher than average (but not that badly).