“After years of grumbling about steadily rising ticket prices, consumers achieved the nearly unthinkable earlier this year: they forced a momentary drop in the average cost of a movie ticket, to $7.86 in the first quarter, down from $8.01 in the fourth quarter of last year, partly by opting out of costly 3-D tickets for movies like “Mars Needs Moms,” and watching films in cheaper 2-D.”