[tet68]

. The plan was to build 1,600 engines to be installed on all Abrams tanks and Crusader artillery vehicles. But the cancellation of Crusader and cutbacks in the Abrams upgrade program drove down the number of engines to fewer than 600.

Why don't they just buy all 1600, shelve 600 as spares, and find 400 other uses for them.

Government today doesn't under stand supply/demand pricing.
Oh, it's so expensive, we can't buy that many.
Ok, now the price is X+.
Oh, that's even more expensive we'll have to cut the order
even more.
Ok, now the price is X++.
OH Oh, now we'll have to cancel the order and start over.

Yee Gods what a way to do things.

[Poohbah]

IIRC, they may not buy "excess sparing" because Congress got slow-rolled more than once through such practices, usually by the Air Force.

The Air Farce would typically be authorized, say, 500 airplanes or missiles of a particular type, when they wanted 700. So they bought, on top of spares for 700 of the weapons system in question, enough spares to assemble 200 more, and then build 'em up at the depot.

Presto! They get the airplanes, and Congress realized (eventually) that they'd been ripped off.