Many service departments have a so called "shop supply" fee, that's added to the bill automatically. Never seen a specific item they were charging for though, unless it was part of the repair itself. It's supposed to cover things like rags, or perhaps some WD40 that was used to lubricate hinges or latch's, type of thing.
Personally, I felt it was a trumped up charge, as this type of thing should have been included in the price for each specific service. They should know what supplies would be needed for any given job.
For example, you go in to have your brake pads replaced, for the price listed on their service menu. Then it's like... "Oh yeah, we needed to add some extra for things like the brake cleaner, and anti-seize we used".. as if they wouldn't know this already..grrrr
Tell them you want to keep the shop towell's, since you paid for them..lol