Moore's law (halving of cost of transistors every 18 months) does not apply here.
Simple physics - storage takes atoms
Atoms equal matter which equal mass
A Quest for Batteries to Alter the Energy Equation - NYTimes.com:
"Automakers need improvements in batteries “everywhere we can get it,” Mr. Miller said.
In 1991 the Advanced Battery Consortium was founded and set a near-term target for developing a battery that would cost $150 per kilowatt-hour of storage. (A kilowatt-hour sells for about a dime and will move a car three or four miles.)
Eighteen years later, prices are in the range of $750 to $1,000. By comparison, a lead-acid battery in a conventional car costs less than $100 for that much capacity, although it is much too heavy to build an electric car around and not durable enough.
Now the Energy Department has a new goal: $500 by 2012.
“We think we can make that,” said Patrick Davis, the program manager at the Energy Department’s vehicle technologies program."
We'll see plug in hybrids on the road, but not because of progress, because of tax policy ... $7500 credit.