The crazy figures don't stop there. UFC superstar McGregor has nearly 25 million followers across Instagram, Facebook and Twitter, while Mayweather has close to 36 million.
Mayweather, who is undefeated, is the strong favourite for the contest which will be McGregor's first professional boxing engagement. He has not boxed since he was an All Ireland youth champion 12 years ago.
Apart from making extraordinary amounts of money, the 40-year-old Mayweather is one of the best defensive boxers in history.
He has won 26 of his 49 fights by knockout and been knocked to the canvas only once, by Carlos Hernandez in 2001. McGregor has a 21-3 MMA record, has never been knocked out, and is the first fighter to hold titles over two divisions at the same time.
While the public may love the contest, boxers don't.
The Independent quoted the legendary Sugar Ray Leonard as saying: "It will be successful, financially. But it is not a fight which will please the boxing purists. The fact that we boxers deliver punches is so different to what they do.
"There's more looping and what have you because they also have to be in position to be able to kick and be on balance to deliver that elbow or whatever shot they have...it's Mayweather by a long shot."