Fueleconomy.gov says it costs $3,550/year to fuel my 2008 Infiniti G37 (at $4.75/gal, premium), and $400/year to fuel my Model S (assuming 15K miles/year). That's a savings of over $15750 over 5 years (assuming the price of petroleum-based fuels doesn't go up, which it will).
The end of oil is near, not just because we're running out, but because we can do better.