Not to be overly nit-picky, you obviously know ASEL referencing the Cirrus but maybe I can add a little more of my own experience. I own a Cirrus SR20, and I'm lucky at cruise to get more than 12-14mpg running 8.5gph lean of peak at altitude. I just recently flew a NA SR22 up to Philadelphia from Tampa and averaged about 12mpg. You might hit those numbers you mentioned in a turbo at flight levels, but not low, and certainly without a tailwind.

The operating costs for my SR20 with all things taken into account: Oil, Hangar Costs, annual inspection and averaged annual repairs, engine overhaul allowance are close to being conservative $160/hr fuel included vs. about $70 about it being fuel alone. From my calculations, if I went with a NA SR22, I'd be closer to $200/hr for a non-turbo, and about $260 for a SR22T.

Keep in mind, those hourly costs don't take into account the capital costs, depreciation and other training expenses required to operate the vehicle.

It's hard to compare costs of a vehicle to an aircraft. To drive to the airport, pre-flight the plane.. file a flight plan and deal with being re-routed the terminal area trying to get into a busy airport often undermine the time savings of just driving, unless i'm flying out of the state. I don't fly because it's convenient or faster. I do it because the feeling of watching the earth drift away from you when the plane is leaving the runway never gets old. I love flying. :)