Blame the boom in demand for ethanol for higher popcorn prices at a theatre near you. Ethanol has pushed up prices for corn and the seed to grow the corn. The company that makes Jolly Time Pop Corn reports price increases of 10 to 20 percent. Other makers report price hikes as high as 40 percent. Still, popcorn remains a blockbuster. Americans consumed 4 billion gallons of popcorn last year.