Costco's expected to take a slice of the pie from Auckland retailers.

The cut-price giant American outfit is moving to a huge site at the Westgate complex.

Costco runs on a membership-model which allows it to offer cheaper products, because it profits from membership fees.

In the US, the cheapest membership is 60 US dollars a year.

First Retail's Chris Wilkinson told Mike Hosking it'll muscle in on existing retailers' territory.

He says Auckland businesses will feel the pinch of competition - but it's unlikely to affect anyone in smaller centres.

It's thought Costco will start building next year, and open in 2021.