[UPDATED] All the estimates you’re seeing on the cost of Das Trumpenwand are leaving something out. Something important. And really, really expensive.

NOTE: I figured out the flaw in my math and have readjusted, using some better numbers suggested by Kristen Kerns Wheeler in the comments.

On Friday my colleague Otherwise suggested we give Trump his wall. This perspective wasn’t received with universal acclaim. But in reflecting on his argument, I found myself focusing on a point that I’m not sure I think is entirely accurate:

Nor did the Berlin Wall keep democracy and capitalism out of the Soviet bloc. It didn’t even do that great a job at keeping people in.

This is both true and false, I think, depending on how you want to define terms.In the long run the Berlin Wall failed, but for 28 years or so it proved fairly effective at keeping people in. Estimates say 5,000 or so escaped, and at least 138 (and perhaps 200) were killed trying. Roughly 100,000 attempted to escape, which means the wall was 95% successful.

Success or failure? You make the call. But one thing seems really clear: whatever success the Berlin Wall had at keeping East Germans in wasn’t about the wall – it was about the shoot-to-kill orders.

Border guards were under strict orders: “Don’t hesitate to use your weapon even when border breaches happen with women and children,” one East German secret service file from 1973 read.

And here’s where I think the story of Trump’s wall hits the epic phase of its unraveling.

The Berlin Wall was 96 miles long (but only 27 of those miles divided Berlin). There were 302 watchtowers – approximately one every 559 yards. (The concentration was a lot higher in Berlin proper, I suspect.)

So there was the wall, but most of the wall was monitored by armed guards. With standing orders to shoot anything that moved.

Let’s compare the Berlin Wall with Trump’s wall.

The projected cost of the Trump’s wall ranges from $12-70 billion. For fun, let’s start with the Washington Post estimate of $25B (because it’s probably the least partisan).

The total length of the border is 1,954 miles. We’ll assume that the wall by itself will be utterly useless because that’s what history tells us, and also because a Mexican congressman already climbed an existing section. Which means for it to be effective watchtowers will be required. Using the Berlin interval of 559 yards per, that would mean Das Trumpenwand would require 6,152 towers (I assume towers because elevation increases visibility – ground-level stations are going to significantly bump the number of watch facilities). I don’t know how much a tower costs, but let’s assume it’s built into the cost of the wall.

Now, you’d need these towers to be manned (or womaned), and you’d probably need three per shift. Three shifts per day. Let’s say you can hire a guard for $50k/year (Federal employee or contractor – according to Salary.com a patrol officer in El Paso earns a median salary of $47,000, and the cost would be higher overall since that’s the cost of the lowest ranking member of the force – sergeants, lieutenants, captains and so on cost a lot more). Add another 50% for benefits – which is standard.

Check my math here, because this can’t possibly be right, can it?

$4,152,600,000.

That’s over 4 billion bucks a year in salary alone?

You could spread the towers out more, you say? That gives the Brown Horde® a lot more potential openings.

You can have two people per tower. Cool – now the cost is down to $2.76 billion a year.

You could use drones instead of people. Oh, really? If you’re doing that, remind me again why we need a wall?

Oh, and by the way – even this approach only works if your guards are willing to shoot to kill on sight (and that only works if we somehow or another decide it’s legal for them to do so). Why? Well, in Berlin more than 3,500 people per year tried to escape knowing they might be shot. And one assumes the fear of getting shot is a deterrent, yes?

Make of this what you will (and by all means correct my math if I’m wrong). But from where I sit, even partisan opposition to Trump’s wall is barely scratching the surface of its problems.