The Costco effect: Auckland supermarket near Costco lowers grocery prices

The opening of the country's newest food retailer Costco is starting to lower grocery prices, but it's very localised.

It's been three weeks since the US bulk-buy giant opened in Auckland's northwest, however, the Costco effect seems limited to one specific geographic area. 

In a massive new shopping area at Westgate, there are at least four competing supermarkets within a few hundred metres of each other.

The newest is Costco and there's a lot of interest in whether it will bring prices down at the other supermarkets.

Pak'nSave shoppers at the store just one kilometre away said it has.

"I've noticed the prices are coming down. A couple of weeks ago I came in to get some chicken and they were changing the prices as I was standing there, and the guy said to me Costco was quite a lot cheaper and people were going there," customer Kim Scrogie said.

"There are a lot more things on special, that they have sort of got similar products," customer Lisa Harkin said.

Shoppers who've been going to both stores said the price drops started three weeks ago - right after Costco opened. 

"Came along to Pak'nSave and found exactly the same brand, and it was two cents cheaper," customer Karen Sanford said. 

She thinks they are price-matching.

So, Newshub tested it with the price of 20 everyday products at Pak'nSave stores across Auckland. 

For about 80 percent of the everyday products we chose, this Pak'nSave was the cheapest, or equal-cheapest. But when it comes to products Costco stocks Westgate Pak'nSave was always the cheapest in Auckland. 

Take Beef fillet, for example, the Auckland average for Pak'nSave was $48.99 a kilo. At Westgate, it's down to $45.99, while Costco's price was one dollar cheaper. 

For tomatoes, Westgate Pak'nSave had the same price of $9.99 as Costco, while the rest of Auckland was more expensive at $10.99. 

And for butter, the store was again the cheapest Pak'nSave in the city at $6.99 but still not quite as cheap as Costco's $4.95.

When Newshub added up the total cost of the 20 identical items across Westgate's three biggest players - Costco came out lowest. 

Countdown was $180, Pak'nSave was $167 and Costco was $151 - a difference of 9 percent below its nearest competitor. 

Pak'nSave said each of its stores is locally owned and focused on low prices.

"Depending on a number of factors including quality, origin and brand, prices of single products do vary and fluctuate by store," they said.

But the real winners are the consumers.

"Increased competition does good things for consumers. So we're seeing it in lower prices on those items where Costco is able to go head-to-head with the duopoly," Consumer NZ CEO Jon Duffy said.

There are a couple of big buts, though.  

You mostly have to bulk-buy at Costco, there's a $60 annual fee and at this early stage the Costco price-lowering effect seems limited to one shop right on its doorstep.  

The retailer has hinted at plans for more New Zealand stores, but until then, those outside of West Auckland will have to wait for some badly-needed competition.