A fascinating survey was publshed by Pike Research (here: http://www.pikeresearch.com/newsroom/48-of-consumers-interested-in-purchasing-a-plug-in-hybrid-electric-vehicle) which found that out of 1,041 respondents, 48% are interested in buying a plugin hybrid car (such as a Chevrolet Volt). The problem is, of those, 65% would pay a premium of an average of 12% over a similar gasoline car, while 35% would not pay any premium at all.
The Volt will cost around $40,000 at first. A 12% premium over on a $25,000 car is $28,000.