if i mess up my math please do say. its likely cause i have a bad headache right now and my logical thought process is a little forgeted
if the wall was 90 yards tall and two feet deep this is what it would cost for the concrete required
height = 30 yards
length = 3500640 yards (length of us/mexican border)
depth = 2 feet divided by 1 yard (aka 3 feet)
height*length*depth = volume of the entire wall in cubic yards
multiply the volume by $80 (1 cubic yard of concrete costs $80) and you get $5,601,024,000 (5 billion. i probably forgeted up my first calculation that i replied to magus with somehow). the depth seems too small though so lets assume that the depth would be 10 feet (3 1/3 yards)
ok lets assume the depth is 10 feet (3 1/3 yards) now
height = 30 yards
length = 3500640 yards (length of us/mexican border)
depth = 3 1/3 yards
run that through the equation again and you get $28,005,120,000 (28 billion) for the concrete cost alone. this is a rough estimate but i would assume that the entire wall would be $100 billion+ with all the other materials and man labor combined. $100 billion+ for a wall that might be entirely useless (remember the drug dealers are good at tunnels and will probably find different ways into the country) seems a little dumb
also remember people will still smuggle in stuff through boats, we can't build a wall out at sea. a wall won't fix problems it'll just move the problems elsewhere.