I said this a few pages back, but I'll say it again.
1. BetOnline is from Australia NOT VEGAS. Vegas cannot take that kind of prop bet. It is ILLEGAL.
2. Books don't post odds based on info (to an extent). They post odds based on where the money is coming in so that they can cover themselves. So, if the money is coming in on the Yankees (which it will b/c they're the yankees and everyone bets on the big boys), they're going to make the odds worse for the Yanks to entice bets being placed on the teams where they have less exposure.