Ben (W), are you telling me that all of the top runners were on commerically available tyres? I know what I saw. Even those on commercial tyres ran multiple sets at $2500+ per set on the weekend.
The bottom line is, superlap is an extremely expensive supersprint with regs that won't allow you to run anywhere else. So for anyone who knows what they are in for, go for it - it is a hell of a spectacle to see. The committment and creativity shown by the serious competitors is great to see.
But anyone who thinks it might be "worth giving a go", or "interesting to try"....either expect to be nowhere in the results, or be ready for disappointment. And huge bills for a once a year event.
Ben (the OP one), there are race events at hidden valley and mallala, if I were you I would go through the CAMS 3D (sports sedan) regulations, make any required mods including a proper roll cage, obtain a log book, and go racing. In terms of outright pace for sports sedans, you would probably be right up there in a local field. Given that you are ~1000klm from either track it would probably only be a few events each year anyway.
BTW good to hear there are more skylines in town now, when I lived up there, there was only 1 other....the SAU NT cruises were pretty shithouse.