In August 2009 I sold my 911 C2S Cabriolet and purchased a GT3 RS. Moving from Austin to Houston had made convertible-ownership much less enjoyable and I'd started to get fast enough on the track that I was hitting the limits of the softer convertible's chassis and suspension. I wanted something lighter and better for the track and the humid Houston weather.
If you are considering purchasing a Porsche of your own then I hope that the information available here is useful to your decision making. While the plural of "anecdote" is not "data", it's often nice to be able to see what another person's experiences have been.Fuel Expenses Track Diary
I've put 47,649 miles on the car since I bought it
Of those, 11,538 have been on the track (24%)
Maintenance has cost an average of $307.37 per month
Repairs have cost an average of $178.40 per month ($0.32/mile).
(I try to keep track-specific spending separate, but I'm sure some costs bleed into the routine spending)