I made up a formula to integrate initial cost of the vehicle into this test and I came out with some numbers. I'm not sure they make sense so let me know if im crazy but anyways, I took initial cost of the vehicle plus (12000 miles divided by average mpg) times (us gas average 5/19 3.791) [i used 3.991 for premium for smart and 4.497 for diesel] here are my numbers. first year of driving your car with the mpg's this site calculated you get.
Toyota Prius $22,453.71
VW Jetta TDI $22,731.77
Ford Focus $17,441.13
smart fortwo $12,787.30
I used the base initial price for each car. I thought it was interesting