Recently, the NY Times had an article about how many models of fuel-efficient cars may take years to justify the extra cost. Here’s a graphic from the article with data from TrueCar:
(I note that the NY Times compares the Prius with the Camry. I still think the Corolla is closer in size. You can see from this side-by-side comparison that in terms of length, width, interior passenger volume, shoulder room, and leg room, the Prius is closer to the Corolla than Camry. Also, does the Lincoln MKZ hybrid really only cost $1,400 more than the regular model and is 15+ mpg better??)
Consumer Reports also had a similar article which discussed how the ultra-efficient “40 mpg” models which were upgrades to the normal versions. The Ford Focus SFE, Honda Civic HF, and Chevrolet Cruze Eco all cost between $495 and $800 more, but the breakeven time when using real-life mpg varied widely between 3 and 38 years.