Another data point for the comparison: the price for 96 octane petrol here just hit NZ$1.729/litre (US$4.15/gallon) and 91 octane is at $1.679/litre (US$4.03/gallon).
It looks like the Ministry of Economic Development is keeping an eye on NZ fuel prices w.r.t. international crude oil prices; it would be nice to see other countries' retail prices included in the graphs too.
According to gasbuddy.com, the average price of regular gasoline (91 octane?) in the USA is $2.898, so it looks like we're paying about 40% more in NZ at the moment.
More scary is this comparison of prices over Europe, denominated in GBP. In the UK it looks like you pay 157% more than in the USA. The cheapest place in Europe to buy fuel is Greece, where you "only" pay 75% more than in the USA. So maybe things aren't that bad here in NZ after all :-)