ante post bets love/battash. If people are willing to take long range (ante-post) selections on horses they have no connection with, they are already taking a huge gamble. So what the bookies actually pocket maybe smaller than what you think.
How often have you watched racing and after the race the prices for the winner has been slashed for said future event. Odds cant be slashed that quick by punters smashing into the winner. Bookies slash prices due to fear and balancing books, they very really take a stand (field) anymore , IMHO