I get all my cellphones on Ebay, for instance: I get high-end models when they're about 2 years old, from high-volume sellers who specialize in refurbished/used cellphones. People are always jealous of my nice phones, thinking I spent $800+ when I usually only spend $100-150.
Many times, if I want something that's only $10 or $20, Ebay is the way to go because I don't have to wait long to get it, and don't have to get $50 worth of stuff to get the "free" shipping, so Ebay ends up being a better deal.
Also, avoiding Chinese sellers is easy on Ebay: just click the box that says "North American sellers only" (or "US sellers only") and you don't have to worry about stuff being shipped from far away and taking a month. Amazon doesn't make it quite so obvious, nor do they allow you to actually exclude such sellers with a search.
Of course, Ebay lets you buy stuff (usually used, or perhaps secondhand but never-used) from non-commercial/individual sellers. Amazon has removed the ability for individuals to resell their stuff unless you sign up for a special seller's account for $35/year.