Hey, I started racing in ITB this year!!
Miata's are the current car to have, but for me, they are out of my budget, even if I built one from an inexpensive streetcar. I got though my two schools and first race for less than 1/2 of the price for the average Spec Miata (includes cost of car, tires, used trailer). Even if the race-to-race operating expenses are minimal (since they are easy on brakes and tires), the initial cost was/is to high.
Todd