You could argue that an iPhone would cost over a billion because you need to develop iOS. But why would you do that instead of modding android for 1/100th of the cost, if you're only gonna make 40?
If not for the insane scale of phones being developed, the components that go into those cheap Chinese phones would be far far far more expensive than they are today.
The military tends to *tighten* the requirements when it’s procuring parts, so more things end up as custom development.
I have no idea what ratio something like an F-35 is for COTS vs custom hardware, though.
Those are technical specs, not quality specs. The quality specs would deal with things like machining tolerances, manufacturer traceability, etc.
Point being, if Pratt & Whitney took a seal design from another aircraft to apply to the F-35, it's not like they aren't already tracking the tolerances, material compatibility, etc. When I worked in aerospace, it was very rare that we went to the machine shop to ask for them to make a bespoke component.