Thanks for the info. My normal method is to find out dealer invoice, subtract out the dealer holdback and any known factory to dealer incentives, and that yields the price the dealership paid for the car. Then, if you can stay within 2-5% of that number, you`ve got a good deal. Problem is, many of these sites are giving you the "average of what others paid", when in reality, that is a terrible method to determine value (if everyone else overpaid... then the average will be higher than it should).
A few websites encourage sending a bid request to all dealers within a 100 mile radius, and see what pops. Then, pit the respondents against one another to earn the sale. That seems like a great shopping method, but a lot of work, especially if dealers are within a narrow range of one another.
That fightingchance.com website promised to give dealer invoice prices, and all factory to dealer incentives (model specific to what the customer wants) for $40. If that is true, it`s easily worth the $40 as it could save thousands off the right car.