As someone above commented, heavy competition among laptop, phone, and tablet makers played a huge role in driving battery prices as far down as they have. Brad, your readers may also value this follow-on piece I wrote, where I looked at how cheap energy storage can get, as a function of the amount of storage we deploy: http://rameznaam.com/2015/10/14/how-cheap-can-energy-storage-get/ Best, Ramez