Indeed, i feel it has a bit of an edge over Amazon in selling slightly odd, not entirely mass-produced things. For example, a while ago, i wanted to grow a couple of plants from cuttings. Just two. To do that, i needed a couple of millilitres of rooting hormone and a couple of peat pellets. No manufacturer packages those things in such small quantities. xxlbigdaves-hydro does, though. He buys big packs of rooting hormone and peat pellets, splits them up, and sells a tiny quantity of both, together. He even throws in a razor blade. Ideal.
More recently, i wanted a very particular make of lipstick for a halloween costume. I could buy a single 2.5 ml tube of it on eBay. On Amazon, you can either buy a big tube, or packs of several 2.5 ml tubes. That's a lot more lipstick than i'm likely to get through in my life.
I'm in the UK, and maybe the sellers here are better than in the US, or Amazon is worse. It probably matters that i am the last surviving human without Prime, so Amazon has a higher marginal cost for me than for the typical Hackernews. And i confess that i use eBay partly out of sheer bloody-minded desire not to see Amazon take over the entire universe.