I wouldn't say that the baths are a sham, but I've only had one once, and I did get lots of different colors out (dark red foam followed by oily dark-green residue). The machines are available on eBay for a couple hundred dollars.
I didn't feel better afterwards, but I did feel... something. really strange, actually, for like a whole day, just kind of out of sorts. And I didn't take a Vitamin C packet afterwards, so that wasn't it.
Give it a try for yourself - you should be able to feel something within one or two sessions and then decide whether you want to spend $200-$300 for a bath of your own.