21% return guaranteed on Mayweather v McGregor?

[Ryan K.]

The Mayweather-McGregor fight is this weekend.  It is a boxing match between one of the greatest undefeated boxers of all time (Floyd Mayweather, 49-0) and a hard-punching UFC star (Conor McGregor, much younger and stronger...but not a pro boxer).  Experts are pretty unanimous that Mayweather wins easy.  Which got me looking at betting lines.

I am not a gambler or sports bettor.  But looking at this, it seems like easy money.  Please correct me if I'm wrong, or join me in flipping a quick 20% this weekend.

It looks like bovada is a reputable online betting place?  Any input for or against?

https://sports.bovada.lv/boxing/floyd-mayweather-c...

Say a guy, through his rentals and property ownership, has been able to accumulate about $20k in expendable money (don't need it to live off, it's building toward the next down payment).

Place $20k bet on Mayweather winning the fight, win $4,444 if this scenario comes true.

Hedge by placing $1,367 on McGregor winning, win $4,442.75 if this scenario comes true.

So, for a total investment of $21,367, by Monday, I'll get a "guaranteed" (both must fight for action) $4,444, or about 20.8% return on investment with no risk and weekend worth of investment timeline.

What am I missing?  This seems too good to be true.