How did the comedy juggernaut Upright Citizens Brigade Theater solve the most intractable problem of live theater today, the inexorable rise of ticket prices?

Simple: don’t pay performers for work onstage.

This unusual business model has helped make the theater one of New York’s premier comedy stages and incubators of talent, showcasing Amy Poehler of “Parks and Recreation” and grooming rising stars like Ellie Kemper from “The Office” and the “Saturday Night Live” cast members Bobby Moynihan and Kate McKinnon.

With the kind of young audience that theater producers have long courted and a bustling school (costing about $400 a class), the Upright Citizens Brigade — which has three sites on two coasts and has inspired competitors like the PIT and the Magnet, creating a new theater sphere in New York — is one of the great success stories of the new comedy boom. But as the theater expands, not paying performers raises questions about not just labor standards but also about diversity and what comedy will look like in popular culture.

Nick Turner, a stand-up performer who quit hosting a popular Upright Citizens’ show over the issue of free work, said that while many improv artists surely benefited from the exposure, others were afraid to speak up.