Fuel economy payback for hybrid vehicles

Chart of years to break even comparing hybrid and non hybrid models given regular gas at $3.85 per gallon and diesel at $4.14 per gallon.

http://www.nytimes.com/interactive/2012/04/04/business/the-cost-of-higher-fuel-economy.html?ref=energy-environment

Given this information it is interesting to note that Chevy Volt sales have increased in March of 2012.
From  1,023 in February to 2,289 in March.  The previous best selling month was December of 2011 when 1,529 were sold.