Mr. Hanson estimated that hotels in the United States collected as much as half a billion dollars in revenue from Internet charges last year.

“I did a meeting a few years ago in a convention center,” said Donna Jarvis-Miller, director of membership and events for the American Public Human Services Association, who said the initial quote for Internet service gave the association sticker shock.

“It was close to $30,000, and that was just to buy out just a section of the convention center we were in,” she said. Now, Ms. Jarvis-Miller said, she brings in her own hot spot network for a small fraction of the cost. “They’ve offered to discount it deeply, but I’m always able to bring it in for less than what they’re offering,” she said of her attempts to negotiate with hotels and convention centers.

Image A mobile hot spot can be transported in a carrier the size of a briefcase. Credit... Matthew Ryan Williams for The New York Times

Even that lofty sum is a relative bargain, though, compared with what some high-tech event producers pay. For the Consumer Electronics Show, which brings about 175,000 people to three convention facilities in Las Vegas every January, the bill for Internet access tops half a million dollars — and that does not include what the show’s 3,600-plus exhibitors spend if they need individual connections in their booths.

“It is expensive and each city has different rates,” said Karen Chupka, a senior vice president for the Consumer Electronics Association.

Factors influencing the rate include what kind of technology is available and how recently it was added, she said, especially if the building is a public facility — as many convention centers are — that is required to choose its technology provider though a bidding process.