$400 ~ $800 depending on what you want ... If you want the top rails done neatly and the top edge of the gate, it adds. If you want ultra durable hard bed liner, it adds. If you want color, it adds. If they have to take off D rings and stuff in teh corners, it adds. You get the idea
If you want to keep the truck from rusting, some say to get the wheel wells bed-linered too ... Have them do the parts of the bed that sit below and outside of the bed floor - front to back.
The truck will weigh a few more pounds, but be quieter and you can just hose it off pretty easily.
You can also get a kit from Al's Bedliner and do it yourself. I paid about $220 for enough to do my boat sole, and in color (light grey). You need to practice on a wheel barrow or something. But once you get the hang of it, it's good.
Professionals doing hard liner use a hot mixer gun. You can't do that at home. I have a bud with a hard Line-X bed with 230,000 miles and he runs a crane service and general construction company. He has one wear-through from a crane block in the back of his truck. It regularly sees diesel spills and all sorts of stuff dropped and banged around back there. Was worth the premium price