Zack O'Malley Greenburg, 3/18/13, Forbes

Jack Black doesn’t have much trouble pulling in hefty paychecks. His band, Tenacious D, grosses about $200,000 per night on the road, according to Pollstar. His film roles, from acting in King Kong to doing voice work on Kung Fu Panda, can fetch far more.

Yet when he comes to the South by Southwest music festival in Austin, Texas—as he’s been doing for many years—he plays for free.

“I’ve never been paid to perform at South by Southwest,” he explained in an interview last week. “It’s something you do to ignite a fire that would hopefully spread across the U.S. of A. And then the next thing you know, we’re on the FORBES list of [freaking] billionaires.”

Black has plenty of company among the festival’s performers. This year’s iteration of South by Southwest is finally over, but during my time in Austin, I was able to ask dozens of artists whether they were paid for any of their gigs at the festival. The final number might surprise some people: zero.

“South by Southwest is about discovering artists,” rapper Machine Gun Kelly told me. “That’s all it’s about, dude!”

The consensus seems to be that a handful of superstars do get paid for big private gigs. One likely example is Prince, who performed at a Samsung event on Saturday night (though a representative from the company would not confirm that the singer, who grosses over $2 million a night on the road, received any compensation for his efforts).

Another gig that many sources suspected of being paid: Jay-Z’s American Express AXP -1.41% show last year. But the artists and executives I interviewed agreed that the vast majority of acts play at South by Southwest for free, and only those of legendary caliber have even a chance at a payday.

Some lucky up-and-comers, like Woodie award winning college band The Lonely Biscuits, find sponsors willing to cover their travel costs. Others get help from their record labels. The rest must find their own way to Austin.

So why spend all the time and money to fly–or take a road trip–to Texas without getting paid? Simply put, it’s exposure. Getting a chance to perform in front of so many industry movers and shakers is worth the financial risk, they figure.

That’s a sentiment with which legendary record executive Clive Davis agrees.

“For my Grammy party,” he says, “I don’t pay anybody.”

UPDATE: According to SXSW representatives, bands that perform at official showcases are given two options for payment–either cash or the artist wristband package, which lets band members attend all music festival activities. About 20% take the cash option. Of those that do, bands are paid $250, while solo acts and duos are paid $100.

Watch to the video below to see some of South by Southwest’s most fascinating personalities explain why they play the festival for free.