We do the work ourselves as well and it is not cheap, stuff breaks and wears like you would not believe sometimes. I mean competitively speaking some of the 944 guys go through a set of tires in 1 weekend.
I mean plan on pads and tires after every serious race weekend at least. Plus compared to track days autocrossing hardly stresses the car, so plan on more parts breaking. And of course the part that people never like to hear, the more your on track the greater the chance of the car being hit by another car, or driver error. Had one of our 944 guys stuff it into a wall b/c another car ran him off at Mid Ohio, completely totaled the car and he has been racing for years and years.