Wow, that is very expensive. My home country built their fence for 22B HUF, about 80M USD, for 175km long. Illegal border crossing dropped from 140.000 a month to some 300, so I would say quite effective. Same kind of fence would be 1400 M USD, for the entire length, and some is already there.
Disclaimer:
Crossing the border legally, or applying for refugee status -> Fine with me
Crossing the border illegally, paying money to human trafficking organised crime -> Nope