I took a look and he does seem to be doing well in terms of feedback and thousands of sales, but I have no idea why it is so expensive for Australia. In fact, when you look at the postage tab, only Australia is in the drop down of countries and, yes, it is $450.99.

I then went to Ebay.com and found his shop there, where it is a completely different situation. The T-shirts have FREE shipping worldwide and every other country (except Australia) is available in the drop down list of postage destinations.

No clue why Australia is singled out, sorry.