I have bough loads of stuff on Ebay from peanuts to up to £1500 I have had very few problems and no unresolved ones,.
Last month I bought a dog of a Samyang 7.5 lens, which was mint looking but decentered. I returned it and got my cash back in a few days. I bought another equally mint but perfect , a few days later.
You can get an Idea of the going price by looking at the "Sold" listings. then have a little patience. I usually have a price in mind and bid with Snipe, to avoid a bidding war, with those who don't know any better.