Absolutely not the ideal weapon to fight them, and better(cheaper) options are coming to shoot down the drones, but until then the price is irrelevant as long as you're preventing loss of human life.
Saving any nonzero amount of lives for any unbounded cost is not necessarily a good trade, if there are ways to save more lives for the same cost, or the same number of lives for a lesser cost.
Saving any nonzero amount of lives for any unbounded cost is not necessarily a good trade, if there are ways to save more lives for the same cost, or the same number of lives for a lesser cost.