This is the first common-sense, fact-based site I've seen on GT prices.
It's got details on production numbers and sales to date, actual current selling prices (from ebay completed auctions), and even a pdf of a graph of how quickly Viper prices dropped after its introduction. (Remember, the Viper was probably as unbelievable in 1992 as the GT is today.
www.FordGTprices.com