Yay, it's cheaper but can it attain higher energy densities for a given volume/weight?
EDIT: Nope
From:http://batteryuniversity.com/learn/article/whats_the_best_battery
"The most economical Li-ion battery in terms of cost-to-energy ratio is the cylindrical 18650 cell. This cell is used for mobile computing and other applications that do not demand ultra-thin geometry. If a slimmer pack is required (thinner than 18 mm), the prismatic Li‑ion cell is the best choice. There are no gains in energy density over the 18650, however, the cost of obtaining the same energy may double.
For ultra-slim geometry (less than 4 mm), the only choice is Li‑ion polymer. This is the most expensive system in terms of cost-to-energy ratio. There are no gains in energy density and the durability is inferior to the rugged 18560 cell."