I know that if we really charged a reasonable per-hour labor charge -- in particular for wooden sailing ships, but also for superdetailed military a/c -- these would be priced out of just about anybody's range. I know that for professional ship modellers, $10,000 is not unusual for a plank on frame ship.
I have done a couple of simple plane-on-frame ships, a couple of fishing sloops and an oyster smack, and I think I figured I made about 25 cents an hour on the labor. But, it paid for my build and bought my next kit.
As for multi-media plastic modeling, I figure up all the materials expenses, including reference books, and charge that amount up front, then arbritrarily charge about the same on delivery. I'm pretty sure I'm selling myself short. But I tend to cram my commissions with every conceivable AM accessory because clients seem to love looking through the magnifying glass and seeing the numbers on the instruments (only works with Waldron in 1/32 or 1/24 as far as I know), or showing them the genuine German rudder pedals, made of stamped stainless steel (again, Waldron) and that dazzles them pretty well. So I figure it's all in the details, after a great build, of course, and I'm not sure I've come close to a great build in my thirty-plus years since that first 59-cent Aurora B-47.
As a sidelight, I once had a roommate who announced one Saturday that he was going to downtown Manhattan, and set up on the sidewalk -- and when I say "on the sidewalk" I mean ON THE SIDEWALK -- with a number of his kits. He set up next to the entrance to a flea market, since he couldn't afford a booth. Hell, he couldn't afford a card table to put his models on, thus they were on the sidewalk on a blanket. Long story short, he sold more than half of them, about ten kits, one for 200 bucks. Until then, they'd been hanging from the ceiling of his tiny apartment for three or four years. He made over a thousand dollars that day selling to passersby. I've never had the nerve to do that, and I can't imagine it happening for me, or for him, had I not seen it with my own eyes. And this guy was, at best, an average modeler who tended to work fast and a bit sloppy by most standards.
TOM