How much of our money does Donald Trump want to pour into his xenophobic fantasy of erecting an impenetrable wall on our Mexican border?

The big-businessman-turned-president insists that costs be damned – just build it! That seems to be a very un-businesslike approach – but then, it’s not his money, is it? For those of you who do care, one measure of what the total tab might be is that he’s now demanding $1.6 billion from Congress to start construction. How much wall will that buy? Seventy-four miles. And how long is the U.S.- Mexican border that he wants to seal off? One thousand, nine-hundred miles long. So, $1.6 billion down and only 1,826 miles to go!

And let’s not even get into the cost overruns, fraudulent billings, shoddy materials and other scams that the army of corporate contractors will add to the sticker price of Donald’s boondoggle on the border.

All of this reckless spending of our tax dollars for a 1,900-mile barricade of both physical and symbolic ugliness that only an extremist minority of Americans support. Besides being wildly expensive, this Trumpian folly is not needed, won’t work, stifles the border economy, crudely tramples on both property rights and sensitive environments, autocratically separates millions of families and communities – and is an insult not only to the people of Mexico, but also to our own people’s democratic values.

As for the assertion by die-hard Trumpateers that a massive, 30-foot high, sixfoot deep, steel-and-concrete barricade will stop illegal immigration from Mexico, here is a fact Congress should ponder before taxing us with this harebrained structure: Two-thirds of undocumented migrants in our country entered with legal visas, then didn’t leave when their visas expired. How does Trump’s goldplated wall stop people who can simply walk through or fly over it?

But Donald Trump loves it when crowds at his raucous right-wing rallies stand and chant in red-faced fury: “Build that wall! Build that wall!” So, he keeps fanning their fire by repeatedly promising to wall off Mexico with a multibillion-dollar “big, beautiful” barrier on the border. “We must have THE WALL” he tweeted in late August, promising again that “Mexico will pay for it.”

The problem with his bombastic presidential promises, however, is that they turn out to be duds, and even Trump knows that his wall promise is a total piece of PR trumpery. First, in a secret phone call to Mexican President Pena Nieto, he admitted he was aware that Mexico actually was not going to pay a single peso for the offensive border barrier. But he begged his cross-border counterpart to stop saying so publicly, for Mexico’s adamant refusal to pay was hurting Trump’s political image of being a strong dealmaker.

Second, even though he loudly threatened on Aug. 21 to “close down our government” if Congress doesn’t pony up billions to fund his pet project, reality intervened just four days later when a mass migration poured across the U.S. border. Not a migration of “bad hombres” from Mexico, but of devastating flood waters from the Gulf of Mexico. Hurricane Harvey’s biblical-level of destruction not only swamped the city of Houston and millions of people in communities all along the Texas-Louisiana coastline – but it also has effectively washed away Trump’s folly of frittering away billions of our tax dollars on a monstrous wall that would be as ineffectual as trying to wall-off the next Category 4 ... or Category 5 hurricane.

Ironically, Trump and his anti-biggovernment congressional cohorts were about to cut nearly a billion dollars from the federal disaster aid budget when Harvey hit the coast. Now, they’ve got to find some $180 billion to add to that budget just to rebuild what Harvey destroyed. Where to get the money? Start by zeroing-out every dime going to Donald’s wall.

Jim Hightower is a national radio commentator, columnist and author.