Figuring out a way to circumvent the rules was the reason for the F1 car being fascinating, and successful. It being a competition involving building the fastest car confirming to the prescribed Formula.
i have a '60s lotus 23, which was built for Le Mans, and it was very low six figures. but an engine rebuild is $30k...
Trackdays skew towards much more modern cars. Although I met the shop that takes care of my stuff at one (they did Spec Miata rental, and now I race that too)