(CNN) The boxing purists are utterly dismissive of the fight as a total mismatch but the fans seem to love the idea, turning out in their tens of thousands just to glimpse the fighters on their promotional tour.
And the increasingly probability is that when that peerless old boxing master of defense -- Floyd Mayweather Jr -- meets the young Irish mixed martial arts prince -- Conor McGregor --- on August 26 in Las Vegas, it'll turn out to be the most profitable boxing match in history. Well at least for a month or so.
Mayweather, who has always liked talking money and is liberally rounded with his figures, told me that he expects to make $300 million (to add to his $800 million career earnings) from this -- his last fight. McGregor says he expects to "quadruple" his net worth.
No wonder Mayweather's long-time business partner, Leonard Ellerbe, has been beaming like the proverbial "Cheshire Cat." Business is looking very good. This is a fight -- so the promoters say -- that the fans demanded and it is evidently selling.
About 10,000 fans turned out at London's Wembley Arena on Friday, largely to see McGregor and salute him on his 29th birthday.
It was a carnival atmosphere -- lots of Irish flags to welcome the former plumber's mate from Dublin -- as well as masks and T-shirts bearing the image of their open-mouthed bearded hero.
A lot of beer was quickly drunk. Noise levels rose -- piped music and crowd singing -- long before either fighter was ever seen.
To a man, they all seemed unperturbed at the prospect of paying $99.95 to see the fight in high definition on pay per view television.
One man had flown over from Dublin just to see McGregor strut his promotional stuff. A friend had already secured him a $2,000 seat (one of the cheaper seats) for the Las Vegas bout.
They just love their man and think he has more than a puncher's chance. Another fan was going to bet heavily on McGregor. He wouldn't say exactly how much, quickly adding "as much as his wife would allow."
McGregor's unshakeable self-belief is clearly infectious. And as the fans all know -- and as the Daily Telegraph boxing correspondent Gareth A Davies put it -- McGregor didn't "just kiss the Blarney Stone, he swallowed it." He can walk the walk and talk the talk.
Mayweather and his entourage needed three 12-seater jets to ferry them around -- from Los Angeles to Toronto, then to New York and finally to London. McGregor and his team had to make do with just one jet.
Almost everything about the tour was predictable -- loud rap music to introduce the warriors, a bit of dancing and posturing by each of them and a welter of expletives. Hardly two sentences were uttered without use of the F-word.
And to ensure perhaps that the media continued to pay attention they cranked up the racial and sexual insults as the tour progressed.
Watching all four events, it got to be very repetitious -- at times dull, crass, offensive and plain silly -- and even the participants seemed to struggle to find new ways of insulting each other.
The ritual face offs turned into pop-eyed pantomime, minders theatrically acting to keep the two men apart for minutes on end.
What was genuinely surprising, particularly to Mayweather's PR people, was how many fans turned out -- estimates of 10,000 in Los Angeles, 15,000 in Toronto and 13,000 in New York -- and all of this without a single punch being thrown.
Everything is very much on Mayweather's terms.
He's the promoter of the fight. This will be a boxing match in a boxing ring (as opposed to Mixed Martial Arts Octagon cage), using 10 ounce gloves and abiding by Marquess of Queensberry rules.
McGregor has never stepped into a boxing ring as a professional. And he hasn't got much time to study "the Sweet Science" as the boxing writer A.J. Liebling famously referred to it.
He won't be able to use his legs to kick his opponent or grapple with him on the ground or use the more concussive four ounce gloves he normally uses.
We can safely assume that we won't be allowed to see McGregor sparring in the gym as he prepares for the fight.
If Mayweather has never been beaten in 49 fights and remains the most elusive of boxers -- he's never been knocked down -- he talked up his own apparent vulnerability. He's 40, hasn't fought in two years and is "ring rusty." He cheerfully points out that McGregor is younger, taller and has a longer reach.
Stephen Espinoza, vice president of Showtime Sports, which will broadcast the fight in the US, told me that five or 10 years ago -- when Mayweather was at his peak -- this fight would've been unthinkable.
Mayweather hasn't stopped any opponent since 2011. But on interview he seemed entirely comfortable with the situation and rather more articulate and thoughtful than the stage trash talk suggested. He remains a calculating boxer and promoter.
The fight remains both fascinating and potentially farcical. Sylvester Stallone -- no less -- has called McGregor "a real life Rocky" and therein lies the fight's appeal.
Could McGregor shock us all and do what every boxer has failed to do -- and knock Mayweather out?
"Mark my words," said McGregor, on the first tour stop in Los Angeles, "I'm going to knock him out in four rounds."
However, boxing aficionados remain skeptical. Indeed they're rather more intrigued by another middleweight fight at the same Las Vegas venue -- on September 16 -- between two of the sport's biggest stars, Gennady Golovkin from Kazakhstan and Mexico's Canelo Alvarez.
The promoter, Oscar De La Hoya has damned the Mayweather and McGregor fight as a farce "that will hurt boxing."
But there's a sense here of trying to reach an audience beyond boxing and mixed martial arts. Espinoza was unapologetic -- he likened the Mayweather-McGregor fight to an event movie -- a summer blockbuster like ' Transformers."
So if works -- if it entertains and makes serious "Benjamins" -- could there possibly be more like it?
The fight game could be subtly changing. Roll Up! Roll Up! for a new kind of circus.