There really isn't a set price, as everything is worth what someone will pay for it....
I use as much information as I can find and then come up with my own price. I get nada.com, kbb.com, Autotrader.com, general internet searches, and the paper to come up with a price. I know that my cars are clean and maintained, so I do go for the upper numbers when selling. Most people don't have a problem with the higher price, if the car is clean. Dealers will low ball your car and hide it in the sale price. You just have to know what price you are going to accept when the deal is done. Then go at the deal and know what you want to pay for something new before you trade it in. I am sure the dealer will not go hungry on the deal.... Anyways, good luck on the sale....