Seems to be true in the higher-end diesels, like the BMWs and Audis and Mercedeses, but the gas versions of cars like the Cruze and the Jetta use regular gas. For people who are cost conscious, I imagine that they'd be looking at the lower-end diesels where the gas equivalents use cheap gas.
Not sure about the Jetta, but the diesel Cruze is so much more efficient than the gasoline version that diesel has to be 1.5x the price of gas for the latter to make sense. EPA cycles tend to underestimate the fuel economy of diesel TDIs and overestimate those of gasoline TDIs. They're pretty accurate for non-turbo gasoline DI engines though.
