I had a similar problem, although it only totaled about 100 CD's. After I made sure I had two compete HD backups, including one in fireproof file cabinet, best bet is to give them away locally. I gave mine away to folks who were more interested in the music then the jewel cases/artwork. I would suggest putting them on a local app like Nextdoor/Craigslist. If you really want to get money for them, you can try setting up a table at a flea market, or hold a garage sale (but you'll get a buck or two for them and not sell them all). Last post them as a collection on sites like this, since there are plenty of folks who will burn them. I know I would if the price was just to cover the shipping and packaging.
Not everyone has streaming and many just like spinning CD's even now and owning the music. Hope this helps a little.