http://www.businessweek.com/articles/2014-03-10/more-pot-les...
That is so much more money than the government has to fight it. Look into how Mexican cartels are actually kidnapping engineers to build infrastructure for their paramilitary operations: http://www.wired.com/2012/11/zeta-radio/
Unless the DEA intercepts practically every drug drone sent across the border, people are going to keep at it. The money's just too good.
1. http://www.pbs.org/wgbh/pages/frontline/shows/drugs/special/...
The DEA's budget is nearly $3B, and they can't do shit against rocks in a bag. The DEA's budget could be $3 Trillion, and they still couldn't do shit against rocks in a bag.
Convictions require evidence.
I suspect that the cartels have already analyzed the cost. I'd bet that an autonomous sub is much more cost effective.