I can see where you come from with the majors or big open shoots for sponsors, but we are talking normal registered shoots. Most of the majors, big opens carry a higher entry fee any way, so who is actually paying for the prize money? It's a bit of a double edged sword really. People complain that prize money never increases, yet they are not prepared to put more in. Yet the majors and big shoots with their higher fee, they will sell out in an instant.
Either way if people want more prize money at normal registered shoots, they will have to stump up the cash.