Professional boxing has a middleweight division, but no economic middle class. Ninety-nine percent of active fighters live in the boxing outhouse, and just a select few make it to the penthouse.

Floyd Mayweather Jr. made $105 million during a 12-month period as the world’s highest-paid athlete, according to a Forbes report published in June, Manny Pacquiao ranked 11th, with earnings of $41.8 million. And heavyweight champion Wladimir Klitschko, armed with his own promotional company, K2, and a rabid fan base in his adopted home country of Germany, ranked 25th, at $28 million. But they are the exceptions in a sport in which many world champions do not accrue wealth.

Seven-figure purses are the norm for boxers in the top economic class of the sport, but only a small fraction of fighters ever see a million-dollar payday. Chris Algieri, the Huntington, N.Y., native who will challenge Filipino icon and WBO welterweight champion Pacquiao in Macau, China, Saturday evening is a rarity. He went from club shows to the sport’s biggest stage in the same calendar year.

With the bout to be shown via HBO pay-per view -- $70 to watch in high definition -- Algieri (20-0, 8 KOs) will make at least $1.5 million, plus an undisclosed slice of the PPV revenue, according to Newsday. Meanwhile, Pacquiao will pocket at least $20 million.

Until this year, Algieri, a former world-champion kickboxer who holds a master’s degree in clinical nutrition, had been scraping by on the fringes of the sport.

“I was making what I felt were lateral moves,” Algieri said in an interview with the New York Times. “I wasn’t making any money to speak of. I was training like a champion, but I wasn’t getting the recognition or getting paid like one. It was making less and less sense for me to stick around.”

In February, he received $15,000 to fight Emanuel Taylor at the Paramount Theater in his hometown and breezed to a unanimous decision win. Four months later, he made his HBO debut as a hefty underdog against Ruslan Provodnikov, as BoxRec noted. He earned $100,000 for the fight, his first six-figure payday, and survived two first-round knockdowns and a grotesquely swollen right eye to eke out a split-decision win.

With that, Provodnikov, who had been seen as a potential Pacquiao foe, was eliminated from the sweepstakes. And Algieri, with his soap-opera star looks, was thrust into the spotlight.

Boxing exists in a different economic universe than do major team sports. There are no unions, no pension plans and spotty medical insurance. Boxers are independent contractors with limited television outlets to showcase their talents.

In the U.S., subscription-based channels HBO and Showtime are the only networks that fork over seven-figure license fees for boxing matches. Although networks such as ESPN2, UniMas and Fox Sports 1 regularly televise boxing, their license fees pale in comparison with what HBO and Showtime pay. So, while Algieri’s bout against Taylor was televised by ESPN2, his HBO debut made him more than six times as much.

And the networks are notoriously limited in their fighter selections. Only 46 fighters have appeared on either HBO’s “Boxing After Dark” or its “World Championship Boxing” telecasts in 2014. Meanwhile, there are more than 18,000 active professional boxers, spread over 17 weight classes, according to BoxRec.

Steve Cunningham, a Philadelphia native and two-time IBF cruiserweight champion, has never made it to the HBO or Showtime promised land. Cunningham won his first title from Krzysztof Wlodarczyk in the latter’s homeland of Poland. He fought in six world title bouts over the next five years, with five of them taking place in Germany.

At the time, Cunningham was a cruiserweight signed to German-based promoter Sauerland Event, a champion in a weight class unembraced by either HBO or Showtime. He defended his belt overseas and made as much as $200,000 for a title defense. Although $200,000 is a nice payday, a boxer has tremendous overhead. In Nevada, a manager is entitled to one-third of a fighter’s purse, while a standard fee for a trainer is 10 percent. That money is also hard to come by without fighting overseas.

After losing his title by unanimous decision to Yoan Pablo Hernandez in 2012, Cunningham moved up to the more lucrative heavyweight division. He’s 4-2 as a heavyweight, including a seventh-round knockout loss to undefeated British contender Tyson Fury. His largest purse as a heavyweight so far has been $70,000 -- far from life-changing money for a father of three, including a 9-year-old daughter with a life-threatening heart ailment.

“The Fury fight made him start to question things,” Steve Cunningham’s wife/manager Livvy Cunningham told Grantland. “You give so much, and you risk so much, and, for most boxers out there, you make peanuts. That was when he first started to question if it was really worth it.”

The promotion for the Pacquiao-Algieri fight has embraced the rags-to-riches story of the challenger. Algieri still lives in his parents’ home in a basement apartment. The $1.5-million man drives a 2001 Honda Accord with an odometer approaching 200,000 miles. Algieri has been milking his everyman persona for everything its worth.

“I like my Honda,” he said matter-of-factly on HBO’s “24/7” series.

But the fight will sell via PPV in America and especially in the gambling paradise of Macau, a two-hour plane ride from the Filipino capital Manila, because Pacquiao moves the needle. He’s a crossover star in a sport whose popularity has declined, in part, because HBO, Showtime and their respective PPV arms have made it less accessible to the average sports fan.

However, PPV has been a financial windfall for the sports’ 1-percenters, such as Mayweather and Pacquiao, as even appearing on HBO does not guarantee instant riches. Established stars like Bernard Hopkins and Juan Manuel Marquez make seven figures, while B-sides such as Algieri take short money, believing that a reputable showing may lead to something bigger.

And so 99 percent of all boxers divvy up meager sums while hoping to one day cash in the way Algieri did. It’s a long climb to the boxing penthouse, and the boxing outhouse remains awfully crowded.