I think this will sell quite a lot of pay per view tickets, as said above, for the (potential) spectacle.
IE: Scenario: Connor, like people expect, can't land a punch. However, he is also physically strong and can take a punch so he lasts a few rounds, but still unable to land any back. He is starting to look a fool compared to all his taunting leading up to the match. Mayweather and crowd starts taunting him as the match goes on. Connor, in a Tyson bites ear moment, flips his shit and goes MMA mode. While most agree that in pure boxing, Mayweather will easily win, most also agree that in a MMA match Connor would destroy Mayweather in seconds, not rounds. Connor disqualified, Mayweather getting the news he won after he wakes up.
Fairly sure that the vast majority buying this isn't buying it for the "this will be a great boxing match", but for a chance the match turns into something else.