Just FYI, it's a few years old but still informative.
http://www.visualcapitalist.com/a-cost-comparison-lithium-brine-vs-hard-rock-exploration/
I also remember reading somewhere (If I could remember I would have posted a link) that brine lithium is the only lithium that they currently make lithium car batteries out of, which is one reason it could be affecting the SP.