The alternative was loading up a Coast Guard ship with guys and sending them out to do an interdiction, seizing 11 men, processing them through the American legal system, incarcerating them for decades, and then eventually deporting them. I bet that costs a couple orders of magnitude more than a drone strike. Arguing cost is not compelling in the slightest.
It's cheaper to drone strike a house with an alleged serial killer in it, than to arrest him and then give him a trial to see if he's actually a serial killer or not.
