I've been keeping a log of all expenses connected with my RX-8. Right now, with 934 miles on the car, the cost of ownership is $36.31 per mile. This includes:

Cost of the Car (no financing, paid cash)
Exhaust Finishers (parts only)
Cargo Net (parts only)
Window Tinting (parts and labor)
Six Oil Filters and Drain Gaskets
12 Qts of Castrol 5W20
MP3 Player (parts only)
$300 to repair a very minor scratch
And, a little gasoline

The cost per mile will obviously drop over time. The incremental cost (gas), however, has only been $0.14 per mile. A bargain!

FYI, on average I've gotten 12.7 mpg. Considering the way I drive, that's not bad. :D

Dave