I've heard this story about the Binion's Million Dollar display, but don't know if true or not --

Nevada Gaming requires each casino to maintain a certain amount of cash on hand to pay winners, in case the "house" has a string of bad luck. There's a formula for the amount of cash required, based on number and type of games / number and type of slots / amount of chips on the tables, etc.

The cash bankroll is rarely required to be used -- unless you're like the old Bird Cage downtown, that had to pay off two keno jackpots in a short period of time (and had to close!).

Anyway, the Binion's cash requirement was around $1,000,000, so that it didn't really cost much in lost interest income, AND they milked the publicity of the Million Dollar Display for years.

Don't know it that's a true story, but if so, Benny was pretty clever in leveraging a NGC requirement into a tourist attraction!