Why do low-budget films charge the same amount at the box office as super-high budget films? In most occurrences, lower production costs translate into lower sales costs. Obviously there are other factors that influence price, including perceived value (affected by advertising), monopolies, and so on.

However there are many companies that produce films that vary greatly in budget. For instance, the Blair Witch Project came out in 1999 with a budget of \$60,000. The same year, Star Wars Episode 1 came out with a budget of \$115 million. That's almost 2000 times more expensive. Yet the two films sat side by side in the box office charging the same amount of money per viewing.

Why don't the makers of super-low-budget films undercut the big budget films?
Opportunity Cost of the Seats

Once the movie is made the cost of production is sunk and irrelevant to the proper pricing of tickets. Only the marginal costs of serving an additional customer and the opportunity cost of showing a different film would enter into ticket pricing. Since cinemas should be setting the number of screens for each movie so that the opportunity costs of the seats are equated across films, this makes them want to charge the same for all films. In support of this idea, I offer that movies do vary in price by time of day. This is a rational response to the perishability of seats (once the movie starts an empty seat for that show is worthless) and time (of day) varying demand for film-going which varies the opportunity cost of the seats by time of day. The theater can't easily equate the opportunity cost across time the way it can across films. 

At the Movies: The Economics of Exhibition Contracts (Filson, Switzer, and Besocke (2004)) provides the following explanation:


  Practitioners provide several explanations for inflexible ticket
  prices. Exhibitors want to avoid menu costs and eliminate consumer
  uncertainty about what the movie will cost. Exhibitors do not increase
  prices of hits because they are engaged in repeat business with local
  consumers, and the potential loss of goodwill from increased prices
  outweighs the potential gain. Charging different prices for different
  movies at multiplexes necessitates employing monitors to ensure that
  consumers see the movies they pay for. Even offering mid-week
  discounts may lead to more time shifting than new demand. Not all
  analysts or practitioners agree that inflexible prices are optimal
  (see Orbach and Einav 2001), although it seems unlikely that such an
  easy-to-exploit profit opportunity would persist. Some practioners
  have experimented with non-uniform prices in  the U.S. in the recent
  past but inflexible prices remain the norm.