Tyler Cowen  links to an interesting post looking at the economics of Lego . The bulk of the post is a hefty, data-filled look at how Lego is actually much the same price as it always has been:
The general trend seems to be that at least in the last couple decades, LEGO has not gotten any more expensive. Let’s next look a little closer into the price of a brick since 1990.
Figure 5 The price per piece of LEGO since 1990 – Adjusted for inflation
Average Real Price Per Piece 1990-2012
From what our data shows, it seems that the notion that LEGO is increasing in price is false at least in regards to the last couple decades. Since around 2006, the average price of a piece of LEGO has remained relatively stable between 10 and 13 cents apiece.
But the best part is the short discussion at the bottom of the post about the secondary market for Lego:
On the website BrickLink  you can find almost any set that LEGO has ever produced. In addition, the site keeps records of trends in the market and value of individual pieces. This site is invaluable to a LEGO collector and has given many the ability to grow their collections. Before the advent of this site and sites like eBay, collecting LEGO required going to garage sales. There are now whole sites dedicated to buying LEGO as an investment , but that is a topic for another article.
If someone is going to do a data analysis of the lego market, this is the one I'd like to see. I'd be particularly interested to find out if there are any arbitrage opportunities left in the Lego world. While the prices of individual second-hand bricks vary wildly, the prices of complete sets are relatively stable, being set by Lego rather than the aggregation of thousands of Lego collectors. That means that it may be possible to buy up sets of Lego, break them up, and sell them for a profit on BrickLink. But, of course, the minute anyone realises that, the value of the pieces will plummet due to oversupply…