It's crazy, I know. I work in government as well, although not defense.
The reason for the prices and the hassle is that the 3rd party in question is contracted to provide the service. They have assurances that the work will be done at a certain level, and more important the contract will have clauses for liability. They in turn will have to have certain items in stock (which costs money), have the qualified staff on call (which costs money), and have the proper insurance in place in case something goes wrong (which costs even more money).
While you were probably more able and more responsive, the truth is that it would have made the brass nervous and set a dangerous precedent. I'm sure they've done their checks on you and that sort, but there was probably no binding contract that governed your activity related to that HW replacement.
80% of the activity at the government is CYA.