Like jdubs said: supply and demand. I seem to remember the principal of 'scarcity' from econ 101. If a good becomes scarce and the demand remains constant or increases, then price increases. I suppose demand could have increased for a very short period following the movie, but i would expect that was a spike and no longer has an affect on demand/price, thus leaving the only contributor to price increase to the limited supply and/or a new, increased demand--generally speaking, of course ;-)
