Cost me $550 for a 8' bed with fifth wheel prep from a rhino liner dealer in March of 2016. It was in the high $400s for a 6'bed but not sure exactly. There is about the same amount of prep work required just not as much spray so price won't change much from bed sizes.
Didn't call anyone else as it was right next door to where I ordered my truck and I wanted the lifetime warranty compared to the 3 yr warranty of the factory one. Not much difference in quality other than they didn't paint over ever screws like the factory did.