It's my theory that when all the externalities are taken into account, cruise ships cost New Zealand's economy far more than they contribute.

Of course there are the environmental costs. They probably outweigh any income on their own. But also, and it's just a 'for instance' every time a big ship docks in Auckland, the ferries are disrupted. On some days they are cancelled for hours which means hundreds of people have to make alternative travel arrangements. If that was fully costed, it would come to thousands of dollars for each docking.

And then there is the admin needed... I'm certain the cost of customs and passport control works out at more than $20 per passenger.