So 1 Trillion Dollars plus 742 Years construction time not including the payment for the workers and engineers
I have a better idea
Mexican-American Border is 3144 km (1934,95 miles)
so we'll hire 3 144 000 Republicans that align along the border and take care of exactly 1m each.
We'll be nice and give them a minimum wage of 10$/h like Trump indicated*
For 4 years + 1 day (leapyear)
24h * 10$ *3.144.000 People * ((365*4)+1) = 1.10241216 × 10^12 $ = 1 trillion 102 billion 412 million 160 thousand Dollars
Verdict: cheaper, better, faster and
3 million new jobs
*
http://www.bankrate.com/finance/jobs...um-wage-1.aspx
*
http://money.cnn.com/2017/02/14/news...-minimum-wage/