People will accept more abuse the lower the price. If I'm buying an overpriced italian car for like $300k, the dealership had better treat me like royalty, offer free oil changes etc. If I'm getting a decent german car for free, the dealership could have an overweight hairy man moon me and fart at me the whole time I'm there, tell me I'm fucking scum, and have a witch curse me to get warts or something. I'd still take it.
The Wii was always cheaper than the other consoles and broke less often than at least the 360 in most cases. I'm guessing that buying an original wii after launch and then the wii mini would still be cheaper than a single 360 for much of the 360's life. And that's assuming you only had to buy one.
(Disclaimer: I rarely used my wii, bought a second 360 after my first one broke, and only switched to PC gaming recently, so I'm a big idiot. Also if a dealership actually had an obese man fart at me, I'd probably get creeped out and leave.)