When The Darkness is open September and October it's making lots of money because this is the time of the year when most people visit haunts. During the rest of the year they don't have to pay makeup artists, actors, security etc like they do during the haunt season. They also aren't using much electric compared to the haunt season because the haunt isn't operational. Plus the rent is a lot cheaper in St. Louis vs Las Vegas. I'm guessing Larry owns the building. You factor that all in and it's much much much cheaper than having a year round haunt on the Vegas Strip. A seasonal haunt is much cheaper to run than a year round haunt for obvious reasons.