JRand, I rarely sell any books either. But I had something like six thousand to move, so I sold a lot of seconds and duplicates of editions that I had upgraded over the years and books that had either been given to me or had been sent to me to adapt into movies or whatever before I left. I went to my and BK's good friends at Bookfellows and they gave me great money for them.
Once I got here, I culled yet another box out of the collection that I didn't really want or knew I'd never read and took them to Half-Price in Cincy. Most of it was junk, but there was some meat in the pile and I think I got a grand total of 13 bucks for it. Barely paid for the gas up there and back. Another friend of mine took some vintage horror and supernatural pp to them and got next-to-nothing. He did much better when he took a box into a local used bookstore here.