The online calculator I used referenced the Bureau of Labor Statistics consumer price index, which said prices in 2018 were 9.37% higher than prices in 2012.
For comparison’s sake, because I’m both curious and nerdy, I used an inflation calculator to determine how The Dark Knight Rises would do in today’s numbers.
That’s not an exact measure, since it’s talking about overall prices rather than specifically ticket prices — which vary theater by theater.