Last week, Mayor Zohran Mamdani’s short stint as a faux president ended with an embarrassing acknowledgment that he could not, as promised during his campaign, arrest Israeli Prime Minister Benjamin Netanyahu.

So, this week, Mamdani the Grocer made a reappearance, with details on the five city-run grocery stores that he will open.

But rather than deliver discount groceries, Mamdani is selling New Yorkers a bill of goods that will cost them millions.

What Mamdani described was a discount food bank dressed up as a grocery. Standing in front of blackboards saying “REDUCED 30%,” Mamdani sounded like a bodega hawker: “Once a month, our five city-run grocery stores will set prices for this core set of goods at 30% below typical retail prices. No exceptions, no gimmicks”

Here’s the most delicious part: the presser was a gimmick from beginning to end.

The mayor promised that “The savings will last for the entire month. That means no weekly fluctuations or sticker shock at the checkout line — not for our seniors living on fixed incomes, nor for the parents who rely on a regular supply of apple slices to keep toddler tantrums at bay.”

The Mamdani markets are new variations of an old New York grift: selling gold watches for $5. The dupes want to believe that somehow this street vendor, surreptitiously displaying watches inside his overcoat, actually found a way to sell “sold gold watches” for just a few bucks.

The math simply does not add up for Mamdani. Most groceries have an average profit margin between 1% and 3%, one of the smallest margins of any industry.

To promise a 30% discount below market rate that cannot be adjusted due to monthly market fluctuations is economically absurd.

It is not a description of a competitive grocery but a public charity. It is a quasi-food bank where taxpayers subsidize the cost.

As usual, Mamdani turns this into a class war, demonizing business owners. He suggests that real grocery stores are simply price gougers hoarding windfall profits from consumers. He ignores that they must pay rent, upkeep and fees — all things the city-run stores may simply write off.

He proclaimed, “May the most affordable grocery store win.”

Of course, the test is not which grocery is the most affordable, but which is the most sustainable. If you are willing to take a bath on sales, you can always offer the most affordable prices for as long as your excess cash holds out.

The first city-run grocery, in East Harlem, will cost $30 million to build — and perhaps more. It will never need to pay this money back nor factor it into its prices. The “warmth of socialism” will cover it; that is, you.

In reality, Mamdani will be selling apples at a far greater cost than any competitor, but those true costs will be buried in the city budget and paid for by the taxpayers.

Indeed, the Mamdani markets are likely prove the most expensive groceries in the city.

Mamdani, however, has never sweated the math or the means. He knows that the focus will be on the cash register price and not the true cost.

Of course, there is a big difference between the gold watch grift and the Mamdani grift: buying a knockoff watch only costs chumps a few bucks. The Mamdani con will cost New Yorkers millions, and most will thank him for it.

Jonathan Turley is a law professor and the best-selling author of “Rage and the Republic: The Unfinished Story of the American Revolution.”