What is a celebrity worth?

“THE WRITER of this piece deserves a big raise,” says Bret “The Hitman” Hart, a professional wrestler from the 1990s. “He is the best there is, the best there was, the best there ever will be,” he adds, echoing his old catchphrase. Your correspondent paid Mr Hart $150 to sing his praises. 

Mr Hart is one of over 10,000 celebrities on Cameo, an online service where anyone can commission famous people to film short messages. Its popularity has surged as celebrities seek new sources of income and confined consumers look for ways to spend money. Last year they paid some $100m for 1.3m videos, more than in the previous three years combined. Talent on the site ranges from Jack Nicklaus, a golfer ($1,000 per clip), and Vicente Fox, a former president of Mexico ($300), to Barkley the Dog, a dog ($5).

Cameo, like Uber, is a two-sided market. But most Uber users don’t care what car shows up, as long as it is clean, safe and gets them to their destination. On Cameo, the emotional connection between a fan and a star matters. “The price that a market will bear depends on the value being created for a potential customer,” says Jill Avery, a professor at Harvard Business School who has studied how online influencers price themselves. But “value” is hard to measure when it comes down to emotion. 

How do celebrities...