Jenna Jameson is one of few to earn a million dollar paycheck in the porn industry. Getty Most people have heard the name Ari Emanuel — the WME super agent who inspired Jeremy Piven's Ari Gold character on HBO's hit show, "Entourage."

The name Mark Spiegler, a top talent agent in a different billion dollar entertainment industry, may not ring as many bells.

That's because Spiegler represents porn stars.

While Emanuel, 51, represents talent such as Charlize Theron and Steven Spielberg; Spiegler, 54, represents top adult female stars with names like Skin Diamond, Chanel Preston and Asa Akira.

Spiegler's boutique firm, Spiegler Girls, represents a small group of elite women and is regarded as one of the industry's top agencies in the Hollywood of porn: The San Fernando Valley.

"We are the buffer — so the girl doesn't look bad. We take the heat," Spiegler told The Hollywood Reporter in their article "Inside the Risky Business of Porn Star Agents."

But while many aspects of the business are changing — from the just-passed L.A. County measure requiring condom use in adult movies to shrinking profits — 40 million to 50 million people in the U.S. are reportedly still regularly watching pornography on the Internet.

"While a decade ago the average female performer would make about $100,000 a year," Spiegler told THR "she now might make as little as $50,000 — all while juggling responsibilities such as social-media outreach and personal appearances."

But for the select few females who make it to the top of the industry, paychecks can be "upward of $350,000 a year, while top male performers can make more than $100,000 annually."

According to Dan Miller, executive managing editor of industry trade magazine XBIZ, there are about 250 "in-demand" women (called "models") who work regularly, shooting between 100 and 150 scenes per year. "A popular girl is going to work a minimum of 10 times per month," he tells THR.

According to Spiegler, there is a relatively straightforward scale for performances by an in-demand actress:

$800 for a girl-girl scene

$1,000 for a guy-girl scene

$1,200 or more for anal sex

$4,000 or more for "double penetration"

According to THR, "guy-on-guy pornography has a separate pay scale; most agents in the mainstream straight porn world, including Spiegler, do not represent gay men."

But for each gig Spiegler books for his girls, he takes 10 to 15 percent, receiving the larger percentage if he also handles transportation for the client.

None of the agents THR spoke with would reveal how much money they personally make in a year, but sources told the trade that top agents can rake in around $250,000 a year from their 10 to 15 percent takes.

"It's very competitive, and the well-known agencies do control most of the talent," added Dan Miller. "It's just like Hollywood in that regard."

And agents don't just handle the financial aspect of a deal, they also help clients set up personal websites, advise them on plastic surgery procedures, arrange for transportation to and from film sets and make sure the actors are staying on top of their mandatory drug and STD testing regimens.

But when it's all said and done, shooting the actual porn films is just a small percentage of an adult film star's job.

According to XBIZ's Miller, "about 70 to 80 percent of an actress' annual revenue is derived from movies, and the remaining 20 to 30 percent could be generated by everything from exotic dancing to sex-toy sales and personal website subscriptions."

One of the most famous adult film stars of all time, Jenna Jameson, earned an estimated $30 million per year hawking her own brand of sex toys until she sold her popular website ClubJenna to Playboy for an undisclosed fortune in 2006.

While Jameson has managed to parlay her career into a mainstream market, other adult film stars argue the pay is simply better on the other side of the 'biz.

Porn star Sunny Leone, a new Bollywood sensation, was paid a lower SAG scale rate for her work on the 2010 Will Ferrell-produced comedy "The Virginity Hit" but made about $250,000 for her role in the adult film "Jism 2."

Now watch porn stars and their agents discuss the 'biz in their own words in this behind-the-scenes video shoot from The Hollywood Reporter:

SEE ALSO: LA County Might Not Actually Be Able To Force Porn Stars To Wear Condoms >