My old company charged 2%, for shop supplies; and during the semi-annual employee meetings, the vice-president and managers still said they were slightly loosing money in that account.

It seemed hard to believe (the 2%), but then you start looking at where some of that money goes, like restocking bolt bin with bolts, washers, nuts, lockwashers, etc. (only to be used when you only needed one or two bolts(for a job) = if more was needed, it need to be itemized, on that invoice.) Other items, like having the wash bay sump cleaned, and the environmental hazardous waste cost to dispose of it. Soap for steam-cleaner and mop bucket to clean shop floor{after each job}, Lightbulbs, for trouble-lights, fuses, cheap electric connectors, welding rods, gases, tips, shop towels, and the list goes on and on.

In this particular case, maybe you should just itemized the actual electrical connectors and heat shrink, then ADD about 5 or 8 minutes, of shop time @ $1.46 per minute, for the additional time it cost (during an actual job) to do the paperwork and wait for a "parts dept. or parts warehouse personnel", to get these small items (more wasted time at $88/Hr), just for these little items, to be invoiced.{thus customer wouldn't see the $22 of shop supplies, BUT sees more dollars, in both labor and parts}

My old foreman, 15 years ago, was pretty good at explaining these "costs" to customers, BUT it sure took time out of his day, to constantly educate customers about shop supplies cost and what ALL it encompasses.