Yeah I've heard lots of stuff about those no-pest-strips. I guess there really is no fail proof method (except never to get mites in the first place or kill them all by hand :P) because someone will always have a problem, or make a problem, and then others will claim its amazing. Just look at the battle between provent-a-mite and black knight. Some swear by the former, others the latter. Crazy.
However i don't really think diluted nix poses much threat to a healthy snake. This person probably used too high a concentration or left the water bowl in, or had a sick snake, I don't know.
Yeah I hear what you're saying about the $ but you can't keep animals and consider 11$ to be expensive. I could see not wanting to pay 50$ for a can of black knight, but you have to be ready to pay. Of course, if a cheaper method exists, go for it.
What do you think of mineral oil?