You've heard it said, I suppose, that movie theaters make most of their profits at the concession stand rather than at the box-office, where distributors chip away at ticket sale revenues. And I'm sure you've had the thought that at $5 (or more) a bag, how can that popcorn not be pure profit, or close to it? This weekend, a bunchofstories have popped up detailing a development I should have anticipated, but didn't: the rising price of corn -- old news, on its own -- has begun to affect movie theater prices, both concession and ticket. AMC, which raised ticket prices in some locations last week, won't cop to corn being the primary cause of the changes, but some smaller chains have been more candid. Prices haven't gone up drastically, but with other recent hikes and the general exhibition-is-dying meme going around, this might not have been the best PR move.