Expect 1200-1600 depending on accessories. Example, if you have a titanium magazine tube, that can't be plated, so the cost is lower.
I built a forum member a high end AR15 that was completely NP3 plated. He took it to a 3 Gun competition and let some of the guys try it out. They stated it shot better than their race guns and it wasn't set up to be a race gun. It had a B.E. Meyers 249 flash suppressor instead of a comp. You could clean it with a paper towel except the bore.