The whole idea is that the buyer and seller would be trying to find a middle groud between paying retail, and getting wholesale. Trade-in is typically the wholesale value of the vehicle. If you wanted to off load the old vehicle quickly, this figure gives the stealership room to do any reconditioning of the car, before putting it on the lot to sell at the retail figure.

If you are a buyer, the "TMV" or private party value represents being able to pay less for the same car, since you aren't having to pay for the stealerships "overhead." As a seller, you get a little more for selling the car outright. As has been said though, you are more than free to put the full retail value, or more, on the asking for your car. If somebody wants it bad enough, they will be willing to pay the price. If not, then the car will sit, and you will have to lower the price to what the market feels the car is worth.