One thing I've learned after trading a lot of cars in is.... the value of a used car at the wholesale level (which is what a trade or sale to dealer is worth) is pretty firm. Ie.. certain year, make, model, mileage, and equipment and any decent used car manager is going to come in within +/- $250 bucks. Some dealers may low ball you or they may "over allow" you if you're trading vs. another purchase. But fundamentally the car price is pretty set. Places like Carmax and Carvana are going to give you a pretty solid number.