"That's a lot of money for 2 hours work", I'd just say "Yes, if only it were all profit". I don't get into justifying things, like that. They don't understand the business side of things, just the amount of money they are parting with, often comparing it to their own income and rate per hour. Another thing they don't realise is how much their employer, is charging per hour for their labour. What they charge per hour at your local garage is much more than they pay the mechanic, it's the same thing.
Dave.