If you want to sell to a guy who you know and refer to as a friend, find a reasonable price and don't worry about what jerks on ebay are asking for. If you want to gauge $600 from an idiot collectard from Craig's List without a care because he isn't really a friend? Fine, see if you can sell out and take him for a ride.
Either way, joining a group with the no intention other than finding out what the most you can hawk your stuff for is rather rude.