For decades, the subway fare and the pizza slice — two New York City commodities — cost almost exactly the same amount. But that “pizza principle” is rapidly disappearing.

As the MTA prepares to increase the transit fare to $3 on Jan. 4, pizza prices across town are substantially higher than the cost to ride the train. The typical price of a plain slice of pizza in New York City now approaches $4, according to a decadelong survey of hundreds of slice joints conducted by this reporter across the city. Pizzamakers and experts who have followed the rising prices point to the COVID-19 pandemic and rising inflation as the cause of the increasing disparity between the price of a subway ride and that of a regular slice of pizza.

The average cost of a slice hovered around $2.54 in 2014, when the subway fare was $2.50, the Gothamist analysis shows. And the trend dates back far longer than that, according to Giovanni Lanzo, who opened Luigi’s Pizza in Park Slope with his father in 1973. Back then, when the subway fare was 35 cents, Lanzo said a slice at his shop cost 30 cents — but also came with a free Coke.

Lanzo, 61, said he sold slices for 40 cents in the late 1970s, when the subway fare was 50 cents, and for $1.75 in 2000, when the fare was $1.50.

"I never thought I'd see pizza slices hit a dollar,” Lanzo lamented. “Now all these places are selling them for $5. Ridiculous."

Two prices began to diverge around 2022, when rapid inflation following the COVID-19 pandemic began to take hold in the United States. The median price of a plain slice now hovers at $3.81, according to visits to dozens of slice shops. A plain slice at popular West Village slice shop Joe’s was $2.75 in 2014. The same slice now costs $4.

Out of the way shops that typically have cheaper slices have also seen price hikes that far outpace the subway fare increases. Tommy's Pizza in Throgs Neck charged $3 for a plain slice in 2023 and now charges $3.50 a slice, significantly higher than the subway fare.

MTA Chair Janno Lieber acknowledged the widening bifurcation at a recent board meeting.

“I don't know what the pizza principle would dictate at this point because folks have told me that we’re less than a slice in many cases,” he said.

“Certainly at Totonno's or some of the other places, great Brooklyn pizzerias that I favor, the slice has gone north of three [dollars].”

While Totonno’s in Coney Island doesn’t sell slices, Lieber’s assessment of the cost of an average slice bears true. According to Jared Lander, a data scientist and professional statistician who has studied the pizza principle, that’s an indication that the cost of a subway ride is a relatively good deal in the grand scheme of things.

“ I actually think it does speak to the MTA as you know, problematic as it might be. They're working hard to keep the price of a subway ride down,” Lander said. “A pizza shop owner can't do that.”

Lander first analyzed pizza data in 2014, and said his analysis excluded dollar slices and other orders that might confuse the calculation.

“Not a pie divided into eight, but a slice of cheese pizza, it was dead on with a good confidence interval right around the cost of a subway ride.”

As both the pizza principle and the MetroCard fade into history, Lander said the past half-decade has fractured the relationship that had held for decades, with inflation hitting ingredients and labor and rent climbing faster than MTA fares. A neighborhood slice joint, however, can't absorb those shocks as easily as a taxpayer-subsidized public agency like the MTA.

“It’s just gotten blown up post COVID with all the inflation hitting the food space, both from raw ingredients and rent and everything that has blown up the cost of a slice of pizza faster than the MTA has raised prices.”

Clayton Guse contributed reporting to this story.