I’m not actually persuaded that this is what is at play, and not just the actual costs for the cinema. You get more popcorn per dollar with the bigger box, but there’s fixed costs incurred in terms of the time of person serving you, the cost of the box, the inefficiency of making a small amount of popcorn, the disposal of waste, etc etc. The cinema might well rather sell 2 large boxes of popcorn than 3 small boxes for this reason.
