Shop supplies???

That's pretty outrageous. I can understand the shop supplies charge in general, if they removed this line item then they would have to increase the prices on parts/labor to cover these related expenses indirectly. But there shouldn't be a charge for shop supplies when no shop supplies are consumed. A wrench to the tensioner is NOT shop supplies.

 

It happens in other industries as well. I work as an Electrical Technician and the company I work for adds a charge to all of our bids to cover overhead such as lighting in our offices, office staff, etc. It's all part of a complicated formula which on-paper looks good but in practice has been a bit harder to enact and frequently requires explanation.