The hybrid Honda Civic gets 50mpg highway and costs $22,000.
At $2.75/gallon for gas, the hybrid costs $0.01375 less per mile. Since the hybrid is $5,000 more, you'll need to drive about 360,000 miles before the hybrid will actually start saving you money.
In the city, the regular Civic gets 30mpg and the hybrid gets 49mpg. This makes the hybrid about $0.03557 cheaper per mile. Even at that rate you still have to drive 140,000 miles before the hybrid starts paying for itself.
Why would anyone buy a hybrid car? Yeah, I guess you're burning less gas, but for $5,000 you can get a nice motorcycle and then _really_ start burning less gas.