Use popsike http://www.popsike.com/ to see what they've sold for in completed auctions-as opposed to any 'price guide', this will provide a real monetary value, i.e. what someone has actually paid.
You can also see completed auctions at ebay ('Advanced Search') though popsike lists those at their site.
You can also see completed auctions at ebay ('Advanced Search') though popsike lists those at their site.