I've seen 100s of millions of dollars spent in my career, and in my line of work I have to say that I cannot state with certainty that one cent of it was spent for any useful purpose. I mean, maybe? That's government and industry both. The DoD and various spook shops were excellent sources of fistfulls of cash, with which they bought things that.. well, they worked. But was the work they were put to useful? Not that I could see.
But that's just one person's experience, one point of view. It sure looks like all large scale bureaucratic enterprises waste money hand over fist, and to figure out who's wasting more you really have to examine the books.
And even the "waste" is employing people, so there's that. The US military may or may not be doing a single damn thing that's worthwhile, based on your point of view, but one thing is for damn sure: they're transferring a crapload of taxpayer money to some of the poorest regions, neighborhoods, and families in the USA, and thereby feeding a hell of a lot of people who would otherwise go hungry.
So, that's good, right?