It isn't done by charging an outrageous labor rate (if you consider 60 - 90/hr reasonable) but rather by spending way too many hours doing it. I had the pleasure of standing there watching on a couple of jobs. I was charged 3 hours labor to paint a 3 x 3 foot patch of bottom paint for example. He actually spent the time, I was right there. But I could have done it in 1/2 hour. Another place, overcharges by about 30% for varnish work. On that occasion I made a note of the comings and goings of the workers. The hours were padded significantly. Once again, they probably went back to the shop, cleaned up with great deliberation and conversation, and billed it off.
Anybody who works on a boat knows that there are many times when the job takes a great deal longer than you thought. Nevertheless I have become very wary of boat yard work on the East Coast, too many jobs done wrong and at great expense.