Like what dane332 said, it really depends on the individual seller. Iv'e actually bought more PC parts new and used through eBay than I ever have through other retailers like Newegg. I just recently bought a used 8GB stick of G. skill DDR3 ram on ebay for no more than $55 and worked just like a new stick. But, again, the best thing to do if your unsure about a particular seller is to check out their seller page and flip through the positive/negative feedback. Always make sure that the seller allows returns in case you receive defective parts! But most importantly buy with caution and read the descriptions carefully, some sellers intentionally leave out information for their own benefit.