BJ, I also don't have the exact figures but I have read many times that the lower the price range the lesser the loss (if you backed em all) that's why with odds on favs you are getting close to a profitable idea. But as Crash says you need to be ruthless, and specialising in this type of betting.
Another idea worth waiting for is to watch the 3 tabs for odds on favs for the place, there was a case at hawksbury the other day odds on paying $1.50 for the win, ran a place and paid $1.40 on one of the Tabs. This does come up fairly often and sometimes actually pays more for the place than it does for the win.