I have the advantage of being retired, so time is not as precious to me.
But I'm on a fixed income, so I have to get value for my dollars.
I drive from Darwin to Melbourne twice each year, and return.
At Xmas, I take the family, and we are on the road for six weeks; the other trip is solo, usually four weeks.
If you have passengers, the cost equation swings in favour of the car.
Big advantages of the drive:
leave when you're ready - no rush to the airport; no hanging around; probably more luggage.
Stop where and when you want - have a good look around in places that interest you.
When you get to destination, you have a car - no need to hire.
Plus - and this is very personal - I actually like driving, and pic-nicking under a shady tree, or counter-lunching in country pubs.
It is possible to be frugal with accommodation - I have had great results through Wotif.com.au, and there are other site.
I don't understand people who spend a lot of money to buy a lovely car, then more money on gadgets - but hardly ever take it out on the highway.
I have an Omega, I spend money on good tyres and preventive maintenance, and I enjoy my drives, and I try to pick a different way home for each trip.
What to take - plenty of drinking water; and keep your phone charged - I use a car-charger. I take an esky - 44 litre is ample for the family. In some parts of Australia, the food on the highway isn't much better than roadkill, so I get a chook and the other components for sandwiches.
There are many, many wonderful places between Geelong & Cairns. If you go in warm weather, you can have a swim at beautiful beaches.