Speaking from experience as a former U.S.A.F. Civil Servant performing duties as a WG-9 Jet Engine Technician, then as a GS 5-10 Material Inventory Control Specialist, and as a Division Leader of the U.S.A.F. QP 4 Program - that the current methods of defining related costs of maintaning Weapon Systems is inaccurate and outdated.
Example: The recycling of used parts into the rebuilding process includes the purchase price of said part as if it is new. An Aluminum/Steel alloy fuel tube on a sub-assembly of a specific system has a high longetivity record and is commonly reused each time a unit from the field is rebuilt. Maintenance, Scheduling, and Planning offices show the rebuilt sub-assembly at a certain cost. They include "Man Hours" and other costs including the price of each used part which have already been paid for.
This in turn drives up the overall cost of the "End Item" returning to the field. Which is all paid for by Tax Dollars in the DOD Defense Budget.
What is needed? An honest change in "Parts Procurement" and Defense Contracting methodology which are the primary drivers of an inaccurate system. Secondly - the "I.G." needs to revamp their inventory diagnostic analysis for a clear and accurate accounting at the end of each fiscal year. Third - Planning, Engineering, Scheduling, and Maintenance "Process Evaluations" from "The Floor Up" need to reassess their formulae for System Rebuild Cost Projections.