The absolute number in the Northeast is Manheim auction, which no matter where you live there is one by you. They control 60% of the used car market world wide. The dealers offer you what the car would sell for at auction. That way they know if it won't sell on the retail side they can cash it there. Can't do that with a book. This week the average price based on many vehicles going through the auction; '04 coupe with 10K on the odo wholesale $19,000, same car with 20K on the odo, $17,276 and the same with 30K miles brought $15,474.