Well taking into consideration that most of their REE are light,...

Well taking into consideration that most of their REE are light, they claim that they can produce at $3/kg.

March 2012 "Molycorp already promises to become one of the lowest cost rare earth producers in the world as its investment in its Mountain Pass mine bears fruition eventually bringing costs down to $3/kg, according to analysts versus around $5.58/kg for Chinese producers."

http://blog.metal-pages.com/2012/03/09/molycorps-1-3-billion-acquisition-of-neo-material-technologies-%E2%80%93-the-deal-that-has-it-all/