Put Solar Cells on top of the container stack (Imported from Mexico. The duty collected on those will be so high that it can pay for the wall. Bingo!!!)
Install a HW electric grid on the containers that is activated on touch, with large warning signs to deterre anybody from even getting close to the wall.
Supply the rest of the power generated to the grid at going rates and the entire project become self-financing, with a hefty profit for the Owner (Trump).
(Minus my 1.5% cut of course)