I don't know about 15 years, since I haven't priced one. But if the Hybrid costs only 10% more than the standard one, and the standard is , say, $30,000. Then the owner must recoup $3000 in fuel savings over ownership.
If the Hybrid gets 32 mpg versus 24 mpg for the standard engine, then that's 8 mpg difference. Using 15,000 miles a year as an average, that means a difference of 156 gallons. So the hybrid owner gets an effective $390/year savings at $2.50 a gallon. Also maybe a tax credit for an electric vehicle.
$3000/390 = 7+ years to break even. That's a long ass time.
Until someone crunches real numbers, and not the ones I guesstimated, and proves the Hybrid will cost less over 5 years of ownership, I will gladly keep my gas eater, than you very much.
I will try and research some real numbers. Now I am curious.