Lithium doesn't weigh much of anything (even compared to oil), so a ton of Lithium is a LOT of lithium. Since as a commodity it's never traded in metallic form (too hazardous and energy-intensive to get it there, and not much market for straight metal, even as an input to battery production). It tends to be traded as carbonate, so a ton of lithium carbonate still has a very small amount of lithium in it. The article…
Current production of lithium is low because demand for lithium is low. Lithium @ 17 ppm is actually more common than Lead @ 10ppm in the earths crust. https://en.wikipedia.org/wiki/Abundance_of_elements_in_Earth...
PS: 37,000 tonns of Lithium are produced in 2012 vs 5,200,000 of lead.