The ‘pizza principle’ had held steady since 1980, but no longer.

Every New Yorker knows one immutable thing about that magnificent city.

While everything else may seem expensive, luxurious or out of reach when you’re barely getting by, you can always count on getting a slice of cheese pizza for basically nothing to keep you from starving during your Big Apple salad days.

Well, not anymore.

A new report has found that inflation has jacked up the prices of fuel, heating, ingredients and labor by so much that a plain slice of pizza now costs more than an average subway fare. 

That cost has been frozen at $2.75 by the Metropolitan Transit Authority to keep New Yorkers moving despite pandemic woes and inflation spikes.

Now, many pizzerias are having break what’s loosely known as the “pizza principle,” an actual economic theory that holds that no matter what else is going on, the price of a plain slice and a subway fare stay equal.

That’s been the case since 1980, with a couple of minor hiccups, but as of this week, its premise has been shattered. 

The average plain slice now costs $3.14 across all boroughs, says Slice, a pizza ordering portal that gets pies to New Yorkers all over.

The most expensive plain slice is, of course, in Manhattan, weighing in at $3.26, though that borough is also more likely have more diehard 99 cent slices that are intent on keeping their prices locked in for as long as they can.

There Is a Loophole, Kinda

Now, most New Yorkers probably have a workaround for that particular dilemma: The monthly unlimited Metro card, which takes them wherever they want for a flat fee of $127.

However, if you can afford that monthly unlimited card, you likely aren’t too financially bothered about a slight increase in plain pizza slice prices.

But that doesn’t mean that they won’t be bummed out by a major economic principle of such a beloved city finally falling flat — although some may be more ready to accept it with that NYC hustle we’ve all grown to love.

One pizza owner told Bloomberg that while he had been selling a plain slice for $3.75, he was about to raise it to $4, betting that the market for slice-lovers will stay sturdy no matter what the outside economic conditions look like.