For a three day pass, your friends would be better to check out the New Zealand Expedia site.
At the current NZ-US exchange rate there is around a $NZ10 saving on the passes that are valid until the end of May, although there are some blockout dates on these, but there is virtually no difference for anything valid after that date.
Credit card and/or bank fees, might make the savings greater if your friends pay in local currency.
Another option, is for them to print out prices from different places and take the quotes to a travel agent. TA's may be prepared to match or better them.