I actually think there are limits to what is allowed to be paid out in a 501-c-3 fundraiser. And I think they are fixed dollar limits, not a percentage. Does anyone have any hard data on this?
Gambling laws are state by state. IRS does not restrict how funds are raised, except that fund raising cannot be targeted to an individual. Washington state requires you to get a license, pay a fee and withhold some taxes in order to hold a gambling event for a fundraiser. You will see the gamut from state to state.