With motor yachts the surveyors charge by the foot generally. In some parts of the country they may charge $10 per foot, so a 40 foot yacht could run $400 for a complete inspection and written report.
MH systems are similar since they also would have a motor, although most bigger vessels have two. Fivers and TTs wouldn't take as much time since there would be no motor/transmission to inspect.
Just thinking of it that way, I would think a MH or Class C would be a $10 per foot charge, a fiver or TT maybe $6 or $7 per foot charge. Wouldn't it take about the same amount of time to inspect a 40' MH no matter if it was priced at $30,000 or $2,000,000?