I worked on several hundred airplanes during my working years and I am aware of what spare parts cost. I'll never understand why the U.S. Government don't set up a crew to dismantle the airplanes in the bone yard and catalog the parts and store them in a safe environment for future use. this is a huge waste of resources. A lot of parts are interchangeable and some are even interchangeable with aircraft s of different manufacturers. Machine parts are especially expensive, and bearings, bushings, and other parts made of bronze, titanium, magnesium, lithium, cost the pentagon dearly to produce.