Many, if not most, costs associated with travel are subject to wild price fluctuations as the providers try to get the most out of their products and services. If you think car hire/rental fees are strange, consider the cost of a coach ticket on a plane which can vary by factors of 3, 4, 5 or more on the same flight. This is because travel providers know, for example, that they can charge top dollar to business travelers who need a particular flight at the last minute and don't have to pay for it out of their own pocket, but must offer substantial discounts to get the casual flier especially on red-eyes, Saturday evenings, and other off-peak times. The same holds true for cars. As Lifey and Donna have pointed out, costs vary from city to city, from firm to firm, from franchisee to franchisee, even from minute to minute.

What you should do then is just what you are doing. Shop judiciously and take advantage of any flexibility you have and categories you might fall in to. Being Australian is one such category. You could be getting a better rate simply because the rental company's experience is that foreigners (or Australians in particular) put fewer miles on their cars than Americans. I know that many companies have started to charge more for a 'local' rental - a car rented to someone who lives in the same city - because these tend to be used for long-haul trips in lieu of the renter's own car. It's the same with one-way fees. They will depend on whatever the franchise's experience has been with getting their cars (the cars are owned by the franchise, not the national company) back from specific cities.

Also, be aware that there are other sources of insurance than just your own auto policy. As noted, check any travel insurance you may have. Check with any motor club, such as AAC, that you may belong to as they may have an insurance scheme which covers you when you rent. Also check with you credit card companies as they, too, will often provide insurance coverage if you charge the rental to them. Only as a last resort, and if it still provides the overall cheapest cost, should you buy short-term insurance from a rental car company.

One last advantage you have is that you might not need to pick up your car at the airport. Such rental locations typically have to charge heavy taxes and other fees levied by local governments to try to get their revenue from 'outsiders' rather than their own constituents. Be sure to check the prices that you can get from off-airport locations in the same city. Often these are at car dealerships or other such sites, and very, very often the difference in price is well worth the cost of the cab fare to get to them from the airport.

AZBuck