City billionaire John Catsimatidis is making his big-screen debut in heartthrob Timothée Chalamet’s newest film, “Marty Supreme” — and, in true form, is making cash off griping about the high cost of things.

“I actually got paid! I’m a member of SAG. And so I got a new career at my age,” the 76-year-old supermarket mogul told The Post on Friday.

“Josh Safdie — who is the big producer on it — he was looking for Upper West Side people and approached me, and I said, ‘Yeah! Sounds like fun!’ ” the mogul said.

Catsimatidis — who is also famous these days for his WABC radio show, where he regularly complains about rising costs in the city — revealed he will star in “two or three scenes” of the new film about the life of a fictional table-tennis star, Marty Mauser.

The inspiration for the main character comes from the life of legend Marty Reisman, who ran a ping pong parlor in an Upper West Side building owned by Catsimatidis, and others who frequented the spot.

The onetime mayoral candidate also makes a cameo in the final seconds of the film’s trailer, which was released Wednesday, in a scene in which Chalamet tries to convince two men with New York accents to purchase a custom orange ping pong ball with his name branded on the surface.

“A custom ball like that, it’s going to cost a lot of money,” Catsimatidis tells the actor.

When it came to working with the Academy Award-nominated Chalamet, Catsimatidis admitted he had no idea who the heartthrob was.

“I never knew who he was! I was complaining to the director that he was getting a bigger role than me!” he quipped to The Post.

It wasn’t clear whether Chalamet, a fellow New Yorker and public-school graduate, knew who Catsimatidis was before filming.

Catsimatidis said his ping pong-peddling scene took as many as seven hours to shoot.

“I would say I’m used to days of work for five days,” Catsimatidis told The Post. “[Filming] was like 14-hour days. By the time I got [done], it was like midnight.”