I bought a pricey 1990 Klein that turned out to have broken shifter/brake lever, cracked seatpost, and missing skewer. When I mentioned this to the seller, he tried to find equivalent replacement parts, which I knew would be futile as they were hard to find in general. He talked to his friend, for whom he was selling the bike, and his friend said, "Tough, it's a used bike, what do you expect?"
I said, "You probably had a pretty good idea that this wasn't going to be going for $300. In the listing, you used the world, "beautiful", "one of the nicest Kleins in the country", your words not mine. I don't expect a cracked seatpost on a bike described as such." I threatened to give negative feedback. This guy nearly a 1000 feedbacks, all positive and I don't think he wanted to break his streak for something that wasn't even his. I did get $200 back I asked for, which was a fair price and if anything, undervalued, but it took more hassle than it should have.