I said exactly the same thing to my partner that it costs us double what we would have spent on 1 week cruise. We just got back from one week in NZ. Time I added the rental car, petrol, accommodation, food, and then all the entry costs (Te Puia was rather pricey at $95 pp in Roturua). And then we had a meal at Cobb and Co (awful worse food we had the whole trip) that was $75 for lunch.
Lot changed at Te Puia. Last time I visited when I was a teenager I remembered that you didn't need to be on guided tour and could just basically walk on the boardwalk track. Times have changed. Its all very commericalised now.