The price difference of some goods between Australia and the rest of the world, is sometimes unbelievable. Photographic goods are stupendously overpriced compared to many other jurisdictions and has been for a very long time.
In 1985 I picked up a brand new Nikon F3 body in Germany, it was not on special, not being moved on by Nikon Germany, just for sale at the regular price. I paid approximately $650 AUD for that camera body. Back home in Australia that exact same body had a non negotiable price of $1,800 AUD plus 32% sales tax for a total price of $2,376 AUD.
Another time, I personally helped someone purchase a 600mm f/5.6 Nikkor lens from New York in a well known store. The difference was literally enough to fund the air fare to New York from Melbourne and back, and with the spare change left over to purchase a very second hand automobile. I did the trip, picked up the lens and with the change left over my friend picked up an old ute (utility vehicle). This was in 1977 when this lens was not imported into Australia, it was a special order as the local importer didn't have it as a stock item.
There was a newspaper article about a youngish Australian photographer who purchased the Nikkor 300 F2. The cost of that lens was more than the average price of a house and land package in Melbourne. If the photographer had been able to purchase this in the USA he would have saved around 50% of the price, but as it was a made to order lens at the time, he opted to get it locally. This was in the early 80's.
Now as to whether or not the collecting of taxes for goods consumed in Australia by people who purchase them via overseas websites makes the cost prohibitive. Well, yes and no. In some instances you can almost pay more if you purchase overseas, but it really depends on what you are purchasing.
In the case of photographic stuff, anything that is bulky, like paper, is generally too expensive to source from overseas. Film is definitely cheaper purchased overseas, sometimes not by much, other times by an unbelievable difference.
As for the problem of the local USA store selling on Ebay, they don't have to do anything, Ebay does the tax collecting as they are the ones selling the goods to the person placing the order. So it is a no brainer for any store or business to sell something via Ebay to anyone in Australia. If a store sells direct, then that is another story, but it is not difficult. An American I know who lives not far from me, sells stuff directly and indirectly to the USA. If directly he knows the tax regime of the various states and his software does it. If selling indirectly via Ebay (or similar) it is slightly easier as he processes it as an off shore transaction thereby not collecting any tax;. Ebay in the USA collects the taxes.
Mick.