I got a snarky response one time. The seller wrote the ad like the items had been purchased from an estate sale which said to me "paid pennies on the dollar." I was interested in something that couldn't be found in a price guide, and I'd been the only one watching for over a year, so I offered about 40% of the buy it now price -- there was no bidding. He called me a "lowballer," said that he charged reasonable prices, and told me he'd give it away before selling it at that price. It turns out the items were from his own personal collection, so I suggested he change "from a collection" to "from my personal collection" to give it the appeal that they had been well cared for and had sentimental value. He went off on me about how he had trained people to be expert negotiators for 20+ years. So I told him how he had contradicted himself because his attitude turned off the only offer he'd ever received and that items in the collectible market are only worth what someone is willing to pay. He still hasn't sold it, and I'm the only one who ever watches it, but I won't send him another offer for it.