The Audiogon bluebook is 100% accurate,when you pay for the service you get a whole lot more than just flat prices,you get to see the exact number of items sold,when they sold,how long it took them to sell & prices for each sale,you also get an averaged worth/value based on all other like sales within a time period.
For new sellers its well worth the money,when i 1st started selling i used the service,i dont need it any longer but years back it made me some quid.