Ok so 2 mile range, say 1.5M for overlapping kill zones, 2000 mile border with Mexico, you need about 1400, for 200K a piece, that's 280M to secure the border with automated sentries. That ain't bad at all! That's pocket change. Of course, we'll need about another 1M for signs that say, 'cross tthis line and be shot.'
landmines are cheaper.the DMZ has plenty of those too.