Just an amusing observation -- at Liam's School; they have a Spring Fun Fair. They sell tickets at the door for 50 cents each. A run around one of the typical big inflated bouncy castle deals goes for 4 tickets.
This thing has two sides; so it can take two children at once. The child enters the right or left side, then runs around some inflated fish, through a tunnel, climbs some stairs and then goes down a 15 foot slide. As soon as the children are going down their slides on the right or left; the next child gets the go-ahead. Takes about 30 seconds (I timed a small sample). So that's 2 dollars per side in 30 seconds; or 4 dollars a side in a minute, working to an easy 8 dollars a minute. This ride was non-stop for the entire time we were there.
Actually now that I think about it, the ride was more a Treasure of the Caribbean; the bouncy castle was just the thing they bounce around in while the parents wait for mid-air collisions that could send teeth flying.
I know it's for a good cause. But that's some serious cash flow.