It depends on the direction of the scratches, If they're ala relatively in the same direction probably means that the original didn't use a truck bed liner. If the scratches are in a lot of different directions there is a good chance that the original owner did have a liner in the truck and now the dealership going to try and sell it to you without the liner and even try to use it as a bargaining chip. Dealers have a saying "as is". They'll use that in order to justify the price of the vehicle. If you do buy that truck and decide to use a drop-in liner water will still get underneath and continue to eat away at the bed. Your best option, and probably only, is to have the bed scoured out and have a spray in liner put in. A spray in liner, a good one, will cost between $500-$600. Who ever is trying to sell you that truck ought to drop it by that much before you even consider buying it.
x2, I've seen some work trucks that had the drop in bed liners in them for years. One of the bed liners had a deep gouge that turned into a tear (they're just thick plastic) that they eventually replaced. When the liner was taken out you were lucky to spot any of the original paint color. I was surprised the bed still held as much weight as it did since it was so damn rusted.
