Thank you all for your responses. We needed to trade in the car because it is just too small for me and my family (I am 6'4" and my teenage sons are already 6' tall). There is not enough rear seat room.
I was just trying to correlate what Edmunds calls the True-Market-Value (TMV) with the money that the dealer was offering.
The dealer's position last week, and he showed us the auction report to back it up, was that 99 Passat's were going for between $800 and $1200. Their initial offer was only $1000. Their final offer was $1800.
When I entered the data for the Passat a few weeks ago, I saw values in the mid to upper-$2000's for a trade in value. (I considered our car to be in "clean" condition). Today, however, I re-entered the value of the car, and its TMV trade in value was only $2113.
This was a significant drop of several hundred dollars in its TMV, so the price we got from the dealer ($1800) was only a couple of hundred dollars different than what we could have fought for.
I understand that Dealers are entitled to offer whatever they choose, but I would expect that in the end the TMV price and the dealer final offer would be spot on. In this case, as of today (2/10/13), it is nearly true, but only because the data in Edmunds dropped significantly. When we closed the deal last week (2/6/13), I had felt we were still several hundred dollars apart, giving me a great detail of concern that we weren’t getting the full value of the car. I still don’t understand how a car value could drop by so much in such a short period of time. As a consumer, we need to have a reliable source for car values with which to negotiate with the dealer.