How much does an average LEGO brick cost to produce?
I found that looking to the website http://www.custompartnet.com/estimate/injection-molding/ is a great help to figuring out how much stuff costs.  



I started with a quantity of 1 million, as Lego would make bricks in huge quantities.
Small envelope of around an inch for the standard brick, 
.1 in thickness on the top is the most, 
looked up the volume online, and
chose the other options logically.  

Material and Production is all we care about, so... 

2 cents + 3.3 Cents = ~5 cents per brick!

It might even be a little cheaper assuming they produce in China.