Will spray-in increase value?...No
Will it hurt the value?...Only if it`s a show truck with paint as nice inside the bed as the rest of the truck
Will it help a sale?...Yes,if the bed is pretty beat or patched up.That`s what I`d do if I had a rough bed.That`s what I`d do if I used the truck.I hang onto mine and get my use out before deciding to sell.I`m not concerned with resale value.I`ve never been disappointed with my wallet watching the tailgate for the last time.I look at every penny as a plus.
There`s always carpet liners and tonneau or bed covers.All beds look good that way

.I`d watch using a bed mat on any truck that sits out.That`ll kill a bed fast.