I was going to order a bicycle component from an Australian seller.

Since it is leaving Australia, won't ever be used in Australia and so on, I thought Australian GST would not be payable. This wasn't clear from the website so I asked them and this is what they said

"Thanks for your email. Prices are in AUD, and inclusive of GST.
Because this purchase will take place from an Australian Business, and shipped elsewhere, it's not an export and as such is not exempt from GST. There may be import duty payable in NZ - but you'll need to check with the relevant department on your end, I'm afraid."

This does not sound correct to me, but what do I know? I am sure others here will have more experience.