That really doesn't address why one is being charged for national bandwidth - why not allow metered free local websites? if the site is locally hosted have some sort of 'logo' the end user can look for to confirm it is unmetered? why don't the ISP's offer a jointly funded 'mirror' project that mirrors high traffic sites to reduce international bandwidth use?
I'm sure there are any number of great reasons to have unmetered access to websites within NZ, however, there are still costs to get that traffic to your door.