Morgs got it in a nutshell.
Double standards are rife with this "organisation".
Why haven't they also considered the SC classes? Plenty of quick street cars there.
WSID are also now segregating cars into either daily driven street cars, or full blooded race cars. What about those in between? Street driven cars that actually run sub-11's? There are plenty of those about.
Further to your post Adam, WSID now have two types of private track hires: Super Sedan to TF (ANDRA compliant) cars can hire the track @550 each to a maximum of 8 cars (totalling $4,400), which would require much better track preparation and hence cost> However, this is less than half the total they will receive for the other type of private track hire: for "street-registered, daily-driven" club cars, who are charged $220 each with a maximum of 50 cars (~$11,000).
Their logic and justifications just do nott make sense no matter which way you look at it.