I sometimes daydream about opening a drive-in theater–until I remember that movie theaters are basically fast-food restaurants that happen to show movies. This was reinforced for me Monday night, before a preview screening of the sardonic comedy “Next Day Air,” when an employee of one of the big theater chains announced that he had ice-cream bites for sale and preceded to roam through the crowd with a cooler.

Theaters make most of their money off concessions, not ticket sales, which mostly go to the studios. So I don’t have a problem with paying for popcorn to support a local business. This weekend, I’m taking some friends to see “Star Trek” at the Skyview Drive-in in Belleville, and I’ve asked them not to bring their own food, because I want the drive-in to get the business (and the snack bar makes pretty good french fries).

At the family-run 19 Drive-in in Cuba, Mo., almost everything on the menu is under two bucks, so I buy extra.

But in the past three or four years, I’ve noticed that the price of my usual order at the multiplex chains–a large diet cola and a medium popcorn, no butter–has almost doubled, from about $6 to more than $10. And because I see about 200 movies a year, I’m starting to feel the pinch.

Theaters place some of the blame on rising prices for corn, which is not only popped but provides the sweeteners for soda.

I like theaters, and I want them to reap some of the benefits of the booming box office, so I’m not ready to be a food smuggler or go hungry. But now, during the lull between the summer-movie explosions, I’ll make sure to rush out to the concession stand to get the free refill that comes with a large soda.