You can't trust the numbers, you can never trust the numbers, when the fight industry mates with television to make money for them both. But Conor McGregor has probably banked a couple of million dollars already, and should bank a fair few million more before he's finished.
The question of his actual sporting achievement is much more debatable. Last Sunday morning, Irish time, he became world featherweight champion in that sphere of mixed martial arts controlled by governing body UFC.
The Ultimate Fighting Championship was launched in 1993. In 2001, it was bought by an obscure boxing promoter named Dana White, in partnership with two Las Vegas businessmen. Shunned by television and banned in most American states, UFC was close to bankruptcy at the time.
One of its early pioneers was light heavyweight champion Chuck Liddell. UFC "had image problems, economic problems, competitive problems and management problems," writes Liddell in his autobiography Iceman.
McGregor took up mixed martial arts (MMA) in 2006. Prior to that he'd spent a few undistinguished years in amateur boxing. He made his MMA debut in February 2007, after which he turned professional. He competed in 14 bouts over the next five years, mostly in Ireland, mainly against Irish opponents. His longest fight lasted over nine minutes, his shortest five seconds. His total time spent in the Octagon (a cage) was some 45 minutes. In February 2013, Dana White offered him a UFC contract. In April, he made his UFC debut.
A single full-length fight in professional boxing will last 36 minutes. McGregor, in other words, had fought the equivalent of 15 rounds of pro boxing when UFC offered him his big break. This would tend to confirm that UFC did indeed have "competitive problems". It simply lacked the competitive depth to be found in most established international sports. The sport was, and still is, in its infancy. In signing for UFC, McGregor wasn't throwing himself in at the deep end. He was swimming in a shallow pool.
And virtually every other professional sport demands a deep foundation. Normally a pro golfer, tennis player or soccer player will have started learning the skills in childhood. He or she will have completed the requisite 10,000 hours by the age of 18.
McGregor's apprenticeship only began at 18. He had no foundation in MMA to speak of. He set about learning it hard and fast over the next five years, but success in UFC did not require 10,000 hours of practice since childhood. It didn't have the global factory system of the traditional sports, with their long-established clubs supplying the thousands of contenders - and the elite few who converge at the apex of this deep, wide pyramid.
Instead, being a mongrel amalgam of various sporting disciplines, UFC gathered up its contenders wherever it could find them: Brazilian jiu-jitsu, wrestling, boxing, kickboxing, judo and other combat sports. It was into this frontier organisation that McGregor arrived in 2013, with his 45 minutes' total fight-time in the Octagon.
After a mere six fights he received his title shot against José Aldo, last weekend in Vegas. Aldo was not standing on the shoulders of giants either: he was the UFC's first and only featherweight champion. McGregor took him out with a single punch on 13 seconds. By other international standards, the Dubliner had climbed a very short ladder to the top.
With Aldo concussed and unable to defend himself, McGregor hit him - twice - with what the commentators called a "hammer fist": a full chop-down onto Aldo's exposed face.
On the undercard earlier that night, various fighters had been pinned to the floor by their opponents and pummelled into the face over and over and over. If the man on top felt his fists weren't sufficiently damaging, he used his forearms for variety: forearm smash after forearm smash into a face already crimson with blood.
The United States senator and former presidential candidate John McCain once described UFC combat as "human cockfighting". And the fights indeed tend to be nasty, brutish and short.
There will always be a mob available to witness human violence and degradation. But UFC seems to be picking up a college-educated, middle-class constituency in its fanbase too.
The American writer Chuck Palahniuk traced this phenomenon in his 1996 novel Fight Club, later adapted for a film that starred Brad Pitt. One of its main themes concerns the suburban young man, enfeebled by his safe, pasteurised existence and looking for some sort of masculine authenticity in unlicensed violence. UFC is licensed violence but it seems to be meeting this need among its many middle-class fanboys.
Maybe, too, McGregor's magnificently sculpted physique also forms part of the attraction for a generation of gym-going young men, seemingly in thrall to some idealised image of a masculine physical aesthetic.
Whatever his core appeal, McGregor is lucratively surfing a big wave in the contemporary pop culture. But in comparison to other global sports he is world champion of a very shrunken universe. If he is world class in anything, it is as a salesman. He is handsomely selling a rather ugly game.
Strip away the money, the television lights, the shock and awe of its marketing: UFC doesn't have a history but it has very long roots in back alleys and bar rooms. It is basically bareknuckle boxing and chip shop brawling.
McGregor is the top rooster in a backstreet chicken hut, the overblown king of a pretty small hill.