Don't know, but if buying, just do a google search and see what various dealers are selling for. An average of all their prices would be a good starting point for negotiating a lower price.
If selling, go to Craigs List and do a search. There again, see what others are selling, and get an average. However ... if the item is still on Craigs List, that means, it's not sold. Either the item is priced too high, or it's just the wrong market for this specific time of year. If it was priced right, right season, and right location in the country, it would be sold, and no longer on Craigs List.
I'd start there.