“There’s an urban legend that’s the nightmare of every restaurant owner in New York,” said Robert Bohr, an owner of Charlie Bird, one of a handful of high-end Manhattan restaurants, including Balthazar and Rosemary’s, that have signed on. “It looks like this: four people, driving through the Lincoln Tunnel at 7:30 on Saturday night, deciding which of their three 8 o’clock reservations they are going to keep.”

The price for a Resy table will be set by the restaurant, at about 10 percent of the average check. Reservations for Tuesday at 6 p.m. will cost less than for Saturday at 8; a corner booth may cost more than a central table. “We see reservations changing from a cost center to a revenue stream,” Mr. Vaynerchuk said.

Image In March, the entrepreneur Sasha A. Tcherevkoff started Killer Rezzy. Credit... Jake Naughton/The New York Times

Still, many restaurateurs are deeply resistant to that idea. Alessandro Borgognone, an owner of Sushi Nakazawa in Greenwich Village, is such a stickler for fair access that even his parents have not been able to get a table since the restaurant received a four-star review from The New York Times in December. “It’s online bribery,” he said of the new pay-for-play model. “There’s no difference between buying that table and palming a hundred dollars to the maître d’.” Mr. Borgognone says he monitors all the apps, and when he finds one of his tables for sale, he goes into the restaurant’s private system and deletes it.

In March, the entrepreneur Sasha A. Tcherevkoff started Killer Rezzy, an app and website that sells reservations obtained with or without the cooperation of restaurants; buyers do not know whether their transaction is authorized or not. He had no intention of causing an uproar, he said, but a social media bloodletting began, bringing accusations of scalping, price-gouging and elitism on him and his business model. He now offers to remove any restaurant from his roster upon request.

But restaurants do not necessarily know that they are on the roster. Last week, Killer Rezzy charged $25 for a table for four in a coveted slot — Saturday at 8 p.m. — at Peasant, in NoLIta, providing the name to give at the front desk. On Tuesday, the restaurant’s manager, Dulcinea Benson, said she had no idea that her tables were being sold online.

“Of course that bothers me,” she said. “We’ve been building up this restaurant and our relationships with customers for years,” she said. All of its 100 seats can be reserved free on OpenTable.