If they are the Knowles plates and you have the complete set, you might get a better price, per plate, selling the set. The buyer doesn't have to pay separate shipping charges on individual plates, something that keeps bids down. eBay is the best place, but there are no guarantees, it's all timing. One time someone might pay $100 for the set and a few weeks later, someone else might pay $30.
My parents were big into Bradford Exchange when these came out and at the time, the GWTW plates were quite popular. When eBay first started to get big, maybe around 1997, they were selling for some good money. Values have crashed since then.