What is obvious is that anyone who thinks a wall is going to solve the problem is someone who has never been to the border or a border crossing and seen the amount of traffic that is crossing both ways 24/7/365. The border is lined with US owned industry that is managed primarily by US nationals who live on the US side of the border and cross the border daily. I did it for 3 years of my life.
Cartels "import" drugs through border crossing points. If you can't stop tons and tons of drugs, how do you think you will stop people? You might slow the tickle but if you do so that will create more demand meaning higher wages for those who cross which will in turn increase the incentive to do so.
It would cost 1000x less and be 100x more effective to simply go after the people that hire undocumented workers here in the states.
The Berlin Wall didn't keep people from leaving East Berlin...and they would shoot people trying to do so. Second, the average "worker" who is crossing to find work has nothing to lose. It costs at a minimum, hundreds if not thousands of dollars to round up and deport someone. They sure as hell aren't paying for it...taxpayers do. Going to spend $30,000/yr to lock them up???
So you catch them and deport them...what have they lost?
The people who have something to lose are those who hire them. If there are no jobs for undocumented workers, they will go home. But as long as the demand is there, they will come....it is no different that the drug market, sex market or any other market. As long as there is a demand, that demand will met with a supply.