From what I can gather, the website I linked you to yesterday offers free shipping, even for overseas - as they don't mention an extra shipping cost for overseas purchases. The terms say
For international orders, please allow 2-4 weeks for air mail delivery (on rare occasions, international delivery can take up to 6 weeks). International customers will be responsible for any import duties, taxes or any other import related costs. For orders delivered with Australia, no import duties will apply.
But things like the taxes and import duties don't ever apply for private purchases - and I doubt you're going to be buying DVD box sets in bulk. Of course, if you're interested - make an order and see if they add any extra charges beyond the currency conversion (because atm, the Australian dollar is worth a little more than the US dollar). The prices of the box sets themselves are almost always the cheapest from this store, too.
Pokemon: Season Three - Johto Journeys | DVD, DVD Genres, Kids / Family : JB HI-FI
Pokemon: Season Four - Johto League | DVD, DVD Genres, Animation : JB HI-FI
Pokemon - Season 7: Advanced Challenge | DVD, DVD Genres, Kids / Family : JB HI-FI
Pokemon - Season 8: Advanced Battle | DVD, DVD Genres, Kids / Family : JB HI-FI
Hmm, well Indigo League box 2 is the second half of season 1, and box 3 is the season 2 Kanto episodes... so stick with the American ones for those or you'll just be overlapping a lot of episodes. As for seasons 4, 7 and 8... you should weigh up whether buying the individual volumes is cheaper than going for the $47 box sets, and the cost of a region-free DVD player. (although considering how expensive some of the US season 3 discs are, you're probably better off getting a DVD player just for Johto Journeys).
Remember, once you've got the region-free DVD player - you can get any of the Australian box sets. And we're actually getting ahead of the US in DVDs now too, we've already got the Zoroark movie and the first half of season 13. While that probably doesn't interest you now - the season where Veronica Taylor makes her inevidable and glorious return to the show will probably be out first here too.