Err Jason, is that an inside joke I am missing out on ?

Karen, your numbers make sense. But only a minority of the population start from an suv AND drive ~ 40K miles/year.

The average driver starts from a vehicle that gets 25 mpg, and covers about 15k miles/year. If you plug these numbers into your calculator, you will see where the EPA gets it's numbers.

And particularly in your case since you chose a HCH, I would suggest a comparison to a regular Honda Civic would be reasonable. Does 45 vs 35 mpg sound about right ?
The same 15K average driver now saves 8 gallons/month by picking a HCH over a regular civic.

If the regular civic is not SULEV, then it is an apples to oranges comparison, but one many an american might make anyway.

I have said it before .. the Prius stands out because it is a BIG car that gets good mileage. Willingness to drive a conventional Civic makes the hybrid proposition much less attractive.