Customers never seen to understand the labor part of the bill. They think we should charge like they get paid. Forget the cost of tools, supplies, and other shop related items that are use during the repairs. The time to repair thing a can rather long sometimes as we fix things that have left undone for so long. As you said we got to undo a lot makeshift repairs; sometimes just to get to real problem.
I just finishing up on an ATV where I spent 4 hours going over it find out just what was wrong and the customer say I just want the carburetor repaired. Another 2 hours getting carb done and putting the brakes and wheels back on. NO brakes, front disc pads are down metal to metal contact, rear brake assembly rust and corroded due someone not putting it back together correctly. The water seals were installed incorrectly, Hand brake cable rusted in place. The repair cost currently is $500 and if I had gotten the brakes done too it was closer to $1400. At least it moves now freely instead having to pull through lock down rear brake.
Customer griping that he only paid $500 for nice 2001 model and expected the repairs to be very cheap. He should took to a shop charges $80-$90 hr instead my $40. Repairs never were cheap on these as they are abused by the users.
Now back to Murray setup. Yes they are low end consumer mowers meant to cut well maintained lawns not of lawns here. About 20 yrs they introduced Bradford pear flowering trees. These are terrible at put roots above ground for the mower decks to hit. I repair a lot deck damage from impacts. I had one deck that the hanger had ripped from the deck that looked like had open a beer can and the pull tab made it most open before breaking. Customer fussed about the costs to repair but was happy. I put over four hours into getting back together. Two yrs later he rips off a gauge wheel bracket and ask if I knew how to weld. 
