Counterfeit cash only has to be good enough to trick a human. It is for this reason that I don't think it would be too long before counterfeiters found a cheap low tech method of creating a similar looking effect.
The notes do cost more to produce, but the extra durability means that they last about 4 times as long (from memory) in circulation, so overall the cost difference is marginal for the government, but is an additional deterrent for counterfeiters.
[1] http://en.wikipedia.org/wiki/Polymer_banknote [2] http://www.rba.gov.au/banknotes/counterfeit/index.html
http://www.theglobeandmail.com/report-on-business/economy/cu...
I do notice that when I had the when the bill was in my wallet that has a money clip (I hate big wallets), and when sat on, it produced a visible crease that's not as prevalent in the fiber notes along side it. Overall, I do see it as being more durable.
As the top post said, it only needs to fool a human, not be perfect.
Is it the security measures, or does the (relatively) small number of places where one can pass Australian currency result in fewer attempts?
US currency is somewhat familiar in a large number of countries, so there are lots of opportunities to get someone to take counterfeits.
I wonder how much in total method after method of trying to stay ahead of the Big Money counterfeiters has cost? Mathematical solutions to the problem of forgery have existed for quite a while, I wish there was more a push for those. (And I'm not necessarily talking about bitcoin either, it's just one of many possibilities.) Of course even just going digital for everything would probably solve a lot of problems, and there are math solutions to keeping different types of anonymity as well.