I haven't been watching recent cases so thes figures are only rough guesses:
While the RAA insurance may cover you for killing someone or makinh someone a paraplegic, aquadripleic + legal costs used to be around $14 million so you would need to buy a top up to cover that.
Also there's a wide variety of risk.
If you are flying out of your own property strip, never carry passengers, and don't allow people near the airstrip and aircraft, then you'd expect the risk to be low.
If you fly out of a busy airport with people milling around airside, gliders stopping on the strip with people on the strip and chatting within a few metres of active powered aircraft and on multiple and conflicting strips, the odds are that someone will forget a safety item and be responsible.
If you don't take the VFRG seriously and don't bother to fly a correct circuit, you could be in a place that someone else hits etc. and that's your negligence.
If you fly out of an RPT Airport the aircraft usig it are so dissimilar that an airprox is a common risk and the payout if you are negligent (as in make a mistake or forget something rather than doing beat ups), could be in the tens of millions.
So it's worth looking at your level of risk rather that just going along with blanket numbers.