Reality Prose has an excellent analysis on the changing price of LEGO bricks over the years and a misconception that cost has gone up. According to the chart above, based on data from BrickSet and adjusted for inflation, the average cost per brick has come down.
So why the perception of high LEGO prices? It might have something to with average piece count and more complex sets.
With the data from the piece price evaluations I was able to also evaluate the average size of LEGO sets each year. As you can see on the chart below, the average size of sets released each year stayed somewhat constant from 1980-1990 until around 2000 which set sizes started to increase. The average set size seems to have peaked in 2008 (which saw the release of the Taj Mahal), but since then it hasn’t fallen to its pre-2000 levels. It seems to have found a new normal around 300 pieces.
But even so, LEGO hasn't stopped making the lower-priced sets. It's just that's there's a wider variety now. Be sure to read the complete analysis. It's a fun one.
Side note: We had some friends over the other day, and someone brought a giant castle LEGO set. I don't know how much it cost, but the hours of entertainment we got for a group of six people? Priceless. [via @hmason]