I'm from Australia and have bought 15 knives from 9 individual transactions from knifemakers here - including some from jawilder (thanks for going the extra mile with service Jason!!

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Shipping is more expensive but I'm cool with that. Sometimes there has been a bit of uncertainty about whether the knife/knives will fit in a standard $25 box or if it will cost more; when that has been the case I have made it known that I am fine with a second fee to make up the difference. One knifemaker has also charged me more up front and refunded the difference. I am cool with either.
Communication really is key. Because Customs can be a minefield in some places it is worth asking the customer if they have checked the legality of the knife being sent. It may also be worthwhile making sure the customer knows about features which regularly cause issues (eg if there is a sharpened clip or a folder which can be flicked open).
As a responsible customer I expect the package to take longer. I expect delays (there has only ever been one) and I feel I should be good natured about anything that could go wrong.
FYI there is a recent thread in GBU about what happens in the case of a Customs seizure, including Paypal rules. It's a bit "worst case if your customer is a child about it".
For what it's worth I have only had one shipping issue; after a couple of months the knives ended up back at the maker's place and are now en route to me again. No big deal.
Also just putting it out there, if anyone has questions about shipping to Australia Im very happy to help if I can. I might not know the answer but I will gladly point you in the right direction.