Butter

We did our supermarket shopping this morning at our local Countdown which is one of two major supermarket chains in New Zealand. 500 gramTararua butter was proudly displayed as a special at $7.30. We did not buy any.
That roughly equates to $4.75 US, €4.45 euro or £3.50 UK.
Just 2km away at The Warehouse, which is undercutting the big 2 supermarket chains with some grocery items, the identical item is $4.00. We bought this.
That roughly equates to $2.60 US, €2.44 euro and -£2.08 UK.
New Zealand is the world's 4th largest producer of butter. Are we being disadvantaged? It seems that way.