Scrap yards generally pay by the pound, so the size of the car typically determines how much it is worth. The exact amount of money a scrap car is worth differs drastically, however.
Also important is whether or not the car is driven in or towed to the yard. Most scrap yards offer less money if the car has to be towed. Scrap yards are more favorable to cars in good working order. Regardless, it is important to do research into a specific scrap yard before taking the car there. Many times different scrap yards offer different prices on the exact same vehicle.