I'd say that's gonna be a tough one. They make all of their money selling to the relatively few haunt owners out there, so giving away either merchandise or cash to those same owners would really cut into the bottom line.
Generally when someone sponsors something it is to reach out to new markets. A haunt prop maker might sponsor a Christmas event say, in hopes of reaching a new group of potential customers.
It's kind of like a beer company having a choice between sponsoring a beer-drinking contest and a car race. The beer drinkers are already paying for the product, so their isn't much incentive to sponsor the first event. But the second might help them get new customers.