We know that as costs for batteries have come down, the costs of plug-in cars have followed suit. Ultimately, Price Moves Metal.

When was the last time the MSRP on a strictly fossil fuel vehicle came down by $5,000 like the Chevrolet Volt did this month? Or the $4,000 off the Focus Electric? Or the $6,400* off Nissan LEAF? (*-with a little de-contenting)

The result of these significant price drops?

The Chevrolet Volt is going to set an all-time record this month for EV sales (at more than 3,000 units), and the new 2013 Nissan LEAF has sold 10,400 units in its first 5 months on the market (2,080/month) – that’s 600 more than it sold in all of 2012.

But at what cost do plug-in vehicles reach parity with the traditional internal combustion engine? To make the ‘top 20