First I would point out that national defense in general is not about shooting stuff but rather defending a nation and its interests. Firefighters, when asked what their job is, many people will respond with, "fighting fires." Ask a fire fighter and he will respond with, "saving lives."
Whether we are squirting water from expensive trucks at a rapidly depreciating building or shooting expensive missiles at inexpensive drones the end result should be the same, preserve human life (the most precious thing on the planet).
When there is a real potential for injury to human life our first concern shouldn't be how much it costs to preserve life but rather ensure it can be done, then afterward seek to do it safely, effectively, and efficiently. Perhaps they could have done it more efficiently. How to do that would be a good discussion indeed. Whether they should put a dollar value on whether to save lives is another thing.
Since both evil exists and accidents happen we will forever be spending money and even risking lives in the pursuit of preserving life, and it is right to do so.