During my military career as an operations analyst I often ran into the issue of whether a weapon must be cheaper than the enemy target it destroys. I used to have a Russian military OR textbook (lost it when my house was flooded) that referred to this view as "the capitalist fallacy."
The point is simple. The relative cost of the weapon and the target is irrelevant. The proper comparison is between the cost of destroying the target and the cost of not destroying it, but allowing it to continue to operate against you. If it's doing you more harm than the cost of destroying it, you need to destroy it, even if that costs more than the target did. Example: using an artillery shell to kill a sniper in a tree. More expensive than the sniper's rifle, but cheaper than allowing him to continue shooting, and a lot cheaper than alternative methods of killing him.