When once I was laid off my jobs and had to somehow pay rent, I put up an ad at the local CSUS and a buyer came along. He got a great deal, with about $100 worth of hardware for $17. Distress sale, back about 1974. A selection of pitons, chocks, and vintage gear. Don't know what he did with it, but many MLC SC sport climbing gear on their packs and elsewhere, it proves they are the experts, at least by them, and to gullible beginners. My bolt kit went too, which I regret for the damage it then might have done (I never placed any bolts except on a home makeshift climbing wall).
I think you may now have to exercise some judgement on who you sell to, it could be a beginner to be used dangerously or stupidly. The MLC SC had a variety of used ropes, and they decided to sell them. Also, the AC had a big fire sale of ice axes and such back when we had to get rid of them (insurance). A Thunderbird ax for $5. They sold out quickly, and many people got great deals. I was going to sell an old rope to a person who would have gotten a real steal, but as he would never use it, except to perhaps impress people, he then figured it wasn't worth it.
By my training, you never buy used ropes from anyone. They don't care what happens to it and you, and in the worst case, you may not be around to say what that seller did to you. Ropes are rated to hold only after 3-4 falls by the IACC (?), and then if they break, they have already done the rated job. Many people don't know that. With the liability waivers and all, they might stick you with some defective gear and declare no responsibility. An over used rope may show no visible damage. They can break, as I've seen. Save yourself and do not spend for used ropes. It's not worth it. And there can be defective nuts, cables, biners, and such, too. They say the buyer beware. I supported my local climbing shop, when we had one. It all helps the economy.