Semi-related: a few days ago I took two boxes of old computer and math books to a local Half-Price Book store. They don't usually offer a whole lot of money for such things, and I had been thinking of donating the books to the public library, but the library didn't seem interested in what I had. I figured I might as well get a few dollars rather than just throw them out.
As expected, after about ten minutes of sorting through what I had brought in, they offered me $13.50 for both boxes, which I gladly accepted. (My goal was clutter reduction, not profit.) A few hours later, they called me on the phone and said that they discovered one of the books I brought was more valuable than they first thought, and wanted to give me an extra $9.50.
I have a vaguely similar story. A few years ago my parents found a box of Apple II books from when I was a kid. I saved a few favourites (my extremely-worn AppleSoft Basic reference manual, and a great circuit-level description of the entire Apple I system.) What to do with the rest?
I spent 4 years working at a second hand bookstore, and I knew that computer books were generally treated as unsellable. Especially old ones.
So I put the box on ebay for $1, with a full list of the books inside. Knowing that this way a wide audience would see them, and presumably I would reach a vintage computer enthusiast who would come, pick them up, and take them away. I wasn't looking to make money, I figured $10 or so would be the price - and a guarantee that the person actually wanted the books.
The box sold for close to $300. The winning bidder was after a ProDOS reference book that I barely realised I even had. I have no idea what the second bidder was after.
Used book stores have a hard time figuring out how much math and computer books are worth. It seems like it was easier to sell them in the early 90s. Later there were so many new books being published during the dot com boom that most stores stopped accepting them. The books were becoming obsolete too quickly.
Powell's technical is a fantastic place. Anyone who goes through Portland should visit both Powell's and Powell's technical, which is a distinct store about a block away.
My wife brings stuff to Half-Price Books periodically, usually getting close to nothing. One time I decided to help her out as we had a lot of old DVDs and CDs we didn't actually use. My wife was extremely excited when they gave us over $80 for everything. I asked about why it was for so much, and apparently a couple of the CDs I had brought in were extremely rare and quite sought after. The only one that I remember was a demo CD with only four songs on it, but apparently it was worth a lot to someone.
As expected, after about ten minutes of sorting through what I had brought in, they offered me $13.50 for both boxes, which I gladly accepted. (My goal was clutter reduction, not profit.) A few hours later, they called me on the phone and said that they discovered one of the books I brought was more valuable than they first thought, and wanted to give me an extra $9.50.
I found that refreshingly honest of them.