You can find serious buyers on Ebay without selling on Ebay.
Some years ago I sold rare, old and OOP books on Ebay as a hobby. I made a lot of money but it took a lot of time which I enjoyed devoting to it. That was before quilting!
I still pick up two or three during the year at estate and yard sales that will make me a good profit selling to serious online bookseller and make them a good profit to resell. I found Machine Sewing Singer bound in the green cloth for .25 at a yard sale a few months ago. I wasn't even looking for books but it was laying in box of books marked .25 each. The going price for it is over $300. I sold it to a seller for $150. He has the hassle of Ebay and online selling and I made more then enough profit for what I spent. There are a lot of newer books that are collectible not just the old ones. Some the book binding and publisher is more valuable then who wrote it. One day I'll find THE book, one that will be the crown jewel of the quest and I'll feel the same way I did when I found my FW just sitting there amid plastic toys and old clothes. I love anticipation!