I agree.. it is a circus.. As a mostly boxing fan, will I be buying it, Yes, lol. I can't resist watching the first of it's kind. The PPV will top Mayweather/Pacman. I think you are being generous with your prediction, I actually think Mayweather wins KO in 3 rounds or less, and I don't even like him, but I can't deny his skill.
MMA fans forget the decades it takes to achieve great boxer hand and foot speed, as well as blistering accuracy. Restricted to boxingn rules, Mcgregor will look like an old man compared to Mayweather.
Mayweather gets a defensive punch KO with Mcgregor never landing a clean power punch. MMA fans will lose a lot of money betting on this one, hyped like there is a chance.