I don't use it, but I'm curious what first class shipping from the US to New Zealand really costs? Not what a merchant charges, just actual costs.
Where I'm headed with this is...... there might be a few other things you can't get, but are common here. Weight is obviously a factor in price, but someone might me able to get some liquid smoke and a couple of bottles of rub to you for the same money you would spend on just the liquid smoke.
Last year a guy in Canada was having problems locating curing salts to make Buckboard bacon.... The cost + shipping was really high. Well, the Hi Mountain Buckboard cure is made in Wyoming and it's in all the stores, so I offered to send him some.
On the customs papers there is a box you check if your package is a gift (less duty charges on their end) and another place for "description" and I wrote down "bacon curing spices". The Postal clerk said "bacon cure?", and I told him "yeah, for Canadian bacon".... He said "you're shipping stuff from Wyoming to a Canadian so he can make Canadian bacon???". Everyone in line cracked up.