Note that in Australia the standard insurance liability (the excess) ranges from $2,450 to $2,750. This can usually be reduced to between $300 to $700 (depending on the car type) for an additional fee of $20 to $26 per day (This is called the Optional Excess Reduction or the Loss Damage Waiver). You will be offered this optional excess reduction when you collect your vehicle (soon you will be able to select this option online).
Please note that some credit cards and travel insurance products will cover the cost of the additional insurance for your rental car. Be sure to check the conditions attached to your travel insurance or credit card after making your rental car booking.