How much would a trip from the U.S to N.Z cost?
I flew from the US to Melbourne last summer. The round trip ticket was around $2500, so figure the airfare to NZ to be around $2700-$3000. After that it will depend upon where you want to stay - hostels are reasonably cheap when compared to hotels, for example. Getting a place that allows you to buy and cook groceries will be cheaper than eating out all the time. You'll also need to factor in travel expenses - will you be able to use public transportation or will you need to take taxis or rent a car? Our hotel bill in Melbourne came to around $3000 for 9 days, IIRC. So figure on spending at least $5K-$7K, depending upon other factors. Try looking up hotel costs on a site like TripAdvisor to get an idea of what you can find cheaply.
Can't you get all that on Trip Adviser or the other one I can't remember right now?