They are doing this drawing with no hold because of the guaranteed action. $250 isnt that much of an entry fee really, but not everyone would partake in such an event. But serious gamblers might do it. Therefore, each of those 200 invitees will probably give on average around $2000-3000 in action over a 10 hour period. Sure some will win, but the house will have paid for the party quite easily.
The casino just 2 hours away from my house gives away $30,000 every Monday night to someone who is present. They have 10 drawings over a 4 hour period and each person must be present or they draw again.