About the only things comparable in profitability are soaps/shampoos/detergents and bottled water. There, the most expensive things are the containers.
“The popcorn sold at movie theaters makes way more money for the operators than the movie.”
Absolutely true. I worked at a four-plex movie theatre back in the early to mid 80’s. I can’t remember the exact margin between cost to make it and the price it was sold at - but it was frickin’ huge!