Drive. Thats what we did. I'm from Canberra so have a 2.5 hour head start, but its doable. Once we set off at 3:30am on saturday and were at the track by 12pm after checking in at the hotel. Its much better to head in the day before though, otherwise your stuffed when you get there.
We ended up spending just around 1100 each for four of us all included, plus fuel to get there and back. Thats grandstand seating obviously.