i think those numbers were set based on canelos popularity, rather than actual odds of winning. bookmakers expect many more bets on canelo to win because of his popularity, so they adjust the odds accordingly to even out the losing money with the winning. i expect them to come down to about 3-1 by fight time. the cotto numbers sound about right.
I've never placed a bet so I don't know how it works. If I place a bet now for JCC Jr at 9-1, then by fight night, it narrows down to 3-1, do I still win at 9 times bet?