True, so how 'bout this: Build a tower every two miles and place a Marine sniper in each with orders to wound on sight. Anyone who is wounded and crawls to the US side has a big "II" tattooed on their forehead. Anyone seen in the kill zone with an II on their forehead becomes a free target. My guess is that it wouldn't take too long before other means would be sought out. My guess is that you could build and maintain the towers for a lot less than $36 million per tower.
Heck, with that much money you could give a Marine a free house, for every mile a Marine homeowner, and a free dog too!
No wait. You could, for $18M a mile, probably pack in eighteen Marines in million dollar homes, and eighteen retired K9’s.