Answer to Ken's question - $8 - $10 per LWL foot per year
Answer to Stu's question - my last haul that I was so happy with included a few intangibles that are impossible to price. I was given 2 gallons of Pettit Trinidad by a guy who owed me a favor. I had no problem with the yard doing bottom paint work, didn't think they'd do an inferior job or anything but that paint did me a lot more good on the bottom than in the can so with their approval I prepped the bottom and painted on 2 coats before they applied their contractual single coat.
They benefited a little too because I was paying a fixed price for a haul and bottom paint and they didn't have to expend labor on the prep work.
So regarding bottom paint, I'd let the yard do it in a heartbeat. The thru-hulls and valves I replaced are another matter. As my background is in fiberglass boatbuilding (worked at 4 SoCal sailboat plants), I'm doing that work to my standards, period. That way I know what sealant is used, how clean the hull is before application of the sealant, how tight everything's made up and where the seacock handles point when it's all done.
Sanding, masking and painting the topsides, same thing. I'm doing it. After begging unsuccessfully I relented and applied the paint with the roll and tip technique rather than my preferred method, spraying. That was a case of their field, their rules, no spraying.