Giving some context to the cost of a Wall I see plenty of discussion about what it might take to build a wall, but no real hard data.  I'm hoping some people with more exposure to the construction industry will step in to provide a better picture. I can do simple math, so here is some basic information on what it might take to build a steel barrier.  Not installed. -- I will make the following assumptions: 1) Simple 40 ft vertical bars of steel, evenly spaced, 30 ft above ground, 10 ft below (should be 20 ft below, but that costs more) 2) 2 horizontal bars along the top to tie the vertical slats together (not enough, but not a mile long ladder either) 3) 3 vertical bars per foot, so 4" between bars (a minimal barrier) 4) Vertical bars are simple 1/2" x 6" rolled steel 5) Horizontal bars are simple 3/8" x 6" rolled steel -- Some known data 1/2" x 6" cold rolled is 10.2 lbs/foot 3/8" x 6" cold rolled is 7.65 lbs/foot Current price of scrap steel is $.04-$.08 / lb.  I'm using $0.10 / lb, which is ridiculously cheap, but easy to scale from there. -- So, we have following (per mile of barrier): 1 vertical bar is 408 lbs 15840 vertical bars weighing 6,462,720 lbs 2 horizontal bars, 10,560 ft, weighing 80,784 lbs -- So for every mile of barrier: 6,543,504 lbs of steel (3271 tons), costing $654,350 at 10 cents a lb. Actual price is probably closer to $2-$3 million per mile for raw materials, no welding, installation, etc.  A billion buys ~400 miles of wall with this estimate. Changing to 50ft vertical bars bumps the numbers to 8,159,184 lbs, and $815,918. So just a ballpark estimate, with some assumptions that could be way off, but something to work with.  Steel bars that are 3/8" x 8" weight the same as 1/2" x 6", so changing around the specifics doesn't always have a large impact on the end results.