"I've made several million dollars in this industry," Autograph Pros. founder Michael Kasmar told ET.
The profitability of the business has led some celebrities to be more hesitant to sign autographs. Pitch Perfect star Rebel Wilson sent a clear message to those looking to capitalize on her signature through a tweet, asking professional autograph hunters to "stop stalking [her]."
Autograph hounds make how much? Inside the big business of celebrity signatures
HOLLYWOOD, CA - MAY 07: Actress Charlize Theron signs autographs as she attends the premiere of Warner Bros. Pictures' 'Mad Max: Fury Road' at TCL Chinese Theatre on May 7, 2015 in Hollywood, California. (Photo by Kevin Winter/Getty Images)
PONTE VEDRA BEACH, FL - MAY 06: Lee Westwood of England signs autographs during a practice round for THE PLAYERS Championship at the TPC Sawgrass Stadium course on May 6, 2015 in Ponte Vedra Beach, Florida. (Photo by Richard Heathcote/Getty Images)
DALLAS, TX - APRIL 30: Victoria's Secret Angel Candice Swanepoel signs autographs for guests as they kick off 'International Bombshells' Day' at Victoria's Secret Northpark on April 30, 2015 in Dallas, Texas. (Photo by Cooper Neill/Getty Images for Victoria's Secret)
DALLAS, TX - APRIL 17: Hosts Garth Brooks (L) and Trisha Yearwood autograph a guitar at the ACM Lifting Lives Gala at the Omni Hotel on April 17, 2015 in Dallas, Texas. (Photo by Larry Busacca/ACM2015/Getty Images for dcp)
Miami Marlins left fielder Ichiro Suzuki signs autographs for fans before a baseball game against the San Francisco Giants in San Francisco, Thursday, May 7, 2015. (AP Photo/Jeff Chiu)
Julianna Margulies attends a ceremony where she was honored with the 2,550th star on the Hollywood Walk of Fame at Hollywood Boulevard on Friday, May 1, 2015, in Los Angeles. (Photo by Chris Pizzello/Invision/AP)
Reese Witherspoon signs autographs at the premiere of "Hot Pursuit" at the TCL Chinese Theatre on Thursday, April 30, 2015, in Los Angeles. (Photo by Jordan Strauss/Invision/AP)
Nashville Predators center Colin Wilson autographs items outside the locker room Monday, April 27, 2015, in Nashville, Tenn. Although the Predators rebounded after missing the playoffs the past two years, they lost the opening round of the playoffs 4-2 to the Chicago Blackhawks. (AP Photo/Mark Humphrey)
Jeremy Renner poses for photographers upon arrival at the premiere for the film 'The Avengers Age of Ultron' in London, Tuesday, 21 April, 2015. (Photo by Joel Ryan/Invision/AP)
Scarlett Johansson signs autographs upon arrival at the premiere for the film 'The Avengers Age of Ultron' in London, Tuesday, 21 April, 2015. (Photo by Joel Ryan/Invision/AP)
Robert Downey Jr. signs autographs upon arrival at the premiere for the film 'The Avengers Age of Ultron' in London, Tuesday, 21 April, 2015. (Photo by Joel Ryan/Invision/AP)
Jon Hamm arrives at AMC's Black & Red Ball to celebrate the final episodes of "Mad Men" at Dorothy Chandler Pavilion on Wednesday, March 25, 2015, in Los Angeles. (Photo by Todd Williamson/Invision for AMC/AP Images)
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"I'm not signing your pics that you sell online," she wrote.
Rebel later explained the move to ET, saying, "We're here for the real fans not the ones that are trying to make money by selling our stuff."
A signature from Rebel can go for as much as $70, which is a solid payday for a scribble on a piece of paper, but pales in comparison to other celebs. An autograph from Mick Jagger could net up to $2,500!
"Getting Mick Jagger to sign anything is nearly impossible unless you're a female and have good looks," Michael explained.
As it's unlikely to bag a whale like Jagger, making a career out of the autograph business takes strategy. For Tyler Manninen in New York, it's all about patience.