From the June 2012 figures, all reported in Canadian dollars (1 NZD = 0.80 CAD) and after having subtracted GST (15%, otherwise included in price).
- 500 grams salted butter: $2.46
- 1 kg mild cheddar: $6.35
- 2 litres standard homogenised milk: $2.27
In all cases, you should probably compare with prices available in major metropolitan Canadian areas; remote areas of New Zealand will have higher prices. Note too that most grocery items wind up being more expensive here because of fixed costs and small markets: broccoli runs $2/head in winter and maybe $1/head in summer ($NZ on all of these, including GST); bread's about $2/loaf; rump steak's usually around $12/kg and scotch fillet, on sale, is usually around $23/kg. Kiwifruit, in season, can be less than $1/kg.
I'm not sure what current Canadian prices are on any of these; unfortunately, there doesn't seem to be any Canadian supermarket that puts its prices online. I wonder why New Zealand is so much more advanced on that one - our supermarket industry is at least as oligopolistic as the Canadian one and the fixed costs of the system can't be spread across as many people.