I charged a bit more than that when threading and chambering from a blank! Which involves a whole lot more effort.
That said, just cuz it's a factory barrel doesn't necessarily mean it will screw right on. I can see two hours to disassemble, take off the old barrel, clean, measure, adjust on the lathe as required to set headspace and possibly even setup and chamber if headspace is short. Oh, yeah, and drink some coffee, can't headspace properly without it. More than 2 hours, not unless he includes the trips to the bathroom from drinking all the coffee!
Not picking on you, but I love how folks don't balk at a plumber coming out and charging $200 just to tell you the sink is backed up but don't want to spend the same to have a 60,000 psi pressure vessel installed that ends up inches away from their face when in use.
