I can find them refurbished by online retailers for around $1000-1100. Yours most likely has an old battery and isn't accompanied by a warranty. I don't know whether the charger is in good condition or not. I would say probably $700-800 unless you find a buyer who is lacking in sensibility. Go down from there if it has screen problems or heavy cosmetic damage. If they may actually need to spend money on battery service, a new charger, or anything else.
You can of course list it higher, but I don't think it's a good value for anyone above that. I'm assuming this is a 15". Also note that like the 2011s they do have some known graphics problems. They just aren't anywhere near as bad as the 2011s. The repair program lasts through the end of this year. After that it's on whoever buys it if the motherboard dies. Depot repair is around $350, so it's not exactly trivial.