I've bought hair care products from eBay. I bought some Salerm 21 once and the seller threw in some sample sizes of Salerm shampoo and rinse or something (I'm not quite sure, I gave them to my daughter). And I bought a case of reconstructor conditioner almost a year ago that I was going to use to make my own UBH-type deep conditioner but I never got around to it. A week or so ago, I finally took a bottle out to try it without mixing it with anything, and I do kind of like it. I think I still want to mix in a few drops of peppermint oil or something but I got the case of 12 for around $10 and that included shipping.
Ebay can be a good place to get stuff that you can't normally find where you are and deals on stuff that you use all the time.
If you have a question about a product, ask the seller. If they don't or can't answer your question(s), I wouldn't bid on their auction. If they do answer your questions, watch the tone of the e-mail. If you sense an attitude, I wouldn't bid on their auction. And I always watch the shipping costs. Before I ordered my Maxiglide (with the free shipping from shop at home), I was shopping for a flat-iron on eBay. Some of the prices were excellent but, after I factored in the shipping costs (some of them wanted $30 for shipping), it pushed it beyond my fiscal comfort zone and, in some cases, made it cheaper just to go up the street to get the same thing.
Anyway, I'm rambling again. I tend to do that some time. Good luck!!