I just thought I'd take a moment here, to document some of what I've found when I choose to look up the known or estimated costs of the sort of wall that certain politicians of the GOP want to see built on the US-Mexico border.
Historically, I can think of two borders fortifications that would be adequate parallels between the sort of wall that these GOP idiots want: The Demilitarized Zone between North Korea and South Korea, and the Berlin Wall. While there are certain reasons that the DMZ might have been the better example to use to estimate costs - the use of military troops from more open governments would probably allow for a better baseline for estimating the manpower costs of maintaining such a border fortification being the biggest one I can think of. Having said that, there is effectively zero official sanctioned communication between the two Koreas - so there's no need for the DMZ to worry much about rail traffic, tourists, or any other large-scale legitimate crossing. For this reason I'm more inclined to base my estimates from the model of the Berlin Wall, instead.
Now, there's going to be someone out there telling me that I'm barking mad to think that the Berlin Wall is a good model to choose - I mean the fortifications of the wall were manned 24/7 with pillboxes guard towers and estimates of thousands of troops being occupied to keep East Berliners from making illicit crossings into the West. But an unmanned wall is going to be worse than useless. We already have significant environmental barriers between the US and Mexico - if the pressure pushing people North from Mexico weren't already terribly strong, there would be no need nor desire to risk having a coyote smuggle one across the desert border - often in atrocious, and life-threatening conditions. The existing segments of wall have already been defeated countless times, by direct measures - not simply people walking past the edge of these existing walls. Tunnels, catapults, rockets, balloons and other means have all been used to get contraband and people across the border. If the proposed wall is not manned, and patrolled, it will not achieve any of the goals that its supporters claim. So the proposed wall will be a manned wall. And given the rhetoric of some of the people supporting this wall, it will be armed with shoot-to-kill orders.
So - the Berlin Wall it is.
The Berlin Wall, according to Wikipedia, was 155 km long. Or just over 96 miles. According to this article from the August 17, 1963 Milwaukee Journal pegs the cost of the then existing wall at $25 million. Now, we're going to ignore that, even as late as the mid-80s the Berlin Wall was in a constant state of flux and continually being improved. We're also going to ignore that the Berlin Wall was constructed in many different ways - only some of the wall being the iconic three point something meter tall concrete wall. For a ballpark figure we're talking about $260,000 per mile to build the Berlin Wall. This doesn't include anything but the physical artifact of the wall, so manning costs and I think weaponry costs are still to be figured. For the purposes of a quick and dirty examination this will work, however.
Inflation counters across the web are pretty consistent when dealing with US dollars. The ones I checked all gave a 2016 value for that $260,000 per mile figure derived above of about $2 million dollars per mile of wall. The US-Mexico border is, according to Wikipedia 1954 miles. At this point, I'm just going to call it a 2000 mile long wall, at $2 million per mile - that's a four billion dollar wall they're talking about. It doesn't figure anything for manning costs.
That same 1963 article claims about 11,000 trooops were involved with manning the positions along the Berlin Wall. That's a Division strength unit being used, or about a company of troops for every mile of fortification. Simply extrapolating that would leave us with a requirement for over two hundred thousand troops to man this money hole.
Let me say that again: two hundred thousand troops. The current size of the US Army is four hundred and fifteen thousand active duty and another six hundred thousand in the various reserve formations. Depending upon how you want to look at it that means that this boondoggle would suck up anywhere from 20% of the Army's personnel to almost 50% of it.
Which brings up another reason that I'm sure these cost figures are low: the housing of the troops required for this wall haven't been accounted for. In an urban environment it's relatively easy to add another ten thousand people without having to worry about building water facilities, waste treatment, housing, cooking, stores, etc- all the things that people need to be healthy and functional. (I don't believe the GOP candidates give a flying fuck about the people manning this boondoggle to be happy. Knowing the way their alleged minds seem to work they probably think that homicidal anger and frustration will make the troops manning this fiasco more effective killers of would-be crossers.)
And again, using the Berlin Wall model - it will still be doomed to failure. I realize that the human costs are beneath the contempt of the politicians putting forward this idea, but those will be abominable. The human cost associated with the current methods of smuggling people across the border is already horrific, and while I'm sure the coyotes will be able to find ways around this proposed wall, too, the risks will be going up. And some people will be losing that gamble. Yet even at its most effective and efficient the Berlin Wall never stopped everyone from making the crossing. Many crossings were later shown up as the sort of daring-do that makes for good TV movies, other crossings were more mundane - but they happened through the whole history of the Berlin Wall.
So, can we stop talking about a wall between the US and Mexico as something that makes sense in any kind of reality?