An accurate estimate, based upon Israel’s cost for completely sealing their border with Egypt. Infiltrators — mostly Muslim African migrants — then decreased from 35,000 in 2014 t0 a mere 26 in 2015.
I agree. As an infrastructure estimator for many years I came up with $8.1 billion for 1,000 miles of wall based on a double 30 foot high concrete wall with a paved road between, lighting, drainage and watchtowers.
Alligators and land mines would be extras.