Note that I'm talking about the TRACK, not a casino. This bet would be a pari-mutuel, not a bet against the house.
Horse racing betting is pari-mutuel, meaning that I'm betting against the other bettors, not the track or a casino itself. A Pick Six ticket can be had for a little as fifty cents, and I will win a share of the total prize pool if it pays off. But I can win a bigger share by placing a larger bet.
So, what happens if I try to place a massive bet that would swallow 99 percent of the pool, even if there happen to be lots of winners? Do they take it, or do they freak out?
Casinos have max bet and max payoff house rules. I'm not sure about horse tracks and I can't find evidence.