Doesn't matter what the cost of the weapon is. It's the cost of the potential damage that matters.

Really good point. In this era of asymmetric warfare, it seems that the United States is now playing the part of the British during the Revolutionary War. If the enemies of the US can force it to overspend to maintain its positions, then every encounter will slowly wear away the US military's "staying power".

Of course I imagine that a lot of, if not most, citizens of the US would be happy to see their government abandon its current role of "World Police", and wind down our occupations in Asia --- especially if those occupations are transforming from "wars of aggression" into "wars of attrition".

Does it make sense to stop a $1 bullet with a $3,000 kevlar vest?

Not at all.

Which is why defense contractors are already building swarms of $100 drones to take down other swarms of $100 drones.