A Few Tennis Pros Make a Fortune. Most Barely Scrape By.

On Halloween night 2019, the Canadian tennis player Vasek Pospisil faced Chris O’Connell, an Australian, in a third-round match at the Charlottesville Men’s Pro Challenger in Virginia. The event was part of the A.T.P. Challenger Tour, a rung below the main circuit in men’s tennis. The match had a minor-league vibe: There were maybe a dozen spectators, and one of them was Pospisil’s coach. The total purse for the weeklong tournament was just $54,000, not uncommon for Challenger-level events. The winner would get $7,200.

Pospisil, a former Wimbledon doubles champion who sometimes sips maple syrup for energy during matches, was playing there as part of his comeback from an injury that sidelined…