Jxk
"[H]as anyone calculated the amount of money per aircraft per year that should be charged in the annual bill for maintenance?"
If you’re operating an approved maintenance facility, part of the approval for an aircraft type is that the organisation has the necessary publications necessary to carry out the work in the scope of work.
While it is one option to pass the direct cost onto the customer I would suggest that most maintenance organisations have one or more general categories of billing, for example, “general cleaning materials” covering the cost of polish etc, or “administration” and it may be better to up the amount the billing people allocate to some sort of general billable category.
In my experience most customers don’t actually know what it really costs to run an aircraft and putting a number next to subscriptions on a bill could cause you all sorts of headaches. There’s bound to be one cleaver chap who wants his books when he goes to another maintenance facility, or as noted above wriggles a finger saying it’s your job to have these books anyway.