There are a lot of dealers that also buy back: California Numismatics, APMEX, Provident Metals, JM Bullion, etc. They post a “we buy at” price next to their products. You call in a sale to them to lock in your price, and then mail your things to them, and get that price. Send the things registered and/or otherwise insured.
On EBAY one can often get a bit over spot.