True you do gain savings on Gas. But My insurance went up by $20 a month. This doens't entirely negate the savings I get on Gas, but it does reduce it. I was told by STate Farm that the increased cost on repairing hybrids was being passed on to me. So I suppose if you were going to figure cost/gain on the Prius you'd need to included the raised insurance premium.

That said, I didn't buy my prius to save money. I bought it for convience (getting gas once a month instead of once a week) and because I'm a technophile and I love all the gadgets that come with it.