Popular wholesaler Costco has put purchase limits on its ultra-cheap butter, restricting each store member to 30 blocks, and still it sold out in under half an hour.

The American grocery giant prices its 1kg block of Kirkland Signature butter at $9.99, about half the cost of competitors‘ blocks.

Amid a public frenzy about a recent jump in butter prices, Costco’s discount blocks have garnered a lot of public attention and drawn crowds into its store in Westgate, Auckland, to empty shelves.

At just over 99c per 100g, Costco’s blocks easily beat prices at nearby grocery stores. New World Hobsonville was today selling 500g Pams Pure Butter for $8.49, making it $1.70 per 100g. The 500g Anchor block was $10.99.

Westgate, Auckland wholesaler Costco has put purchase limits on its Kirkland Signature butter, restricting customers to 30 blocks at a time. Photo / Grace Xin Yin Wu

Pak’nSave Westgate, just under 1.5km around the corner from Costco, was today selling the Pams Pure Butter 500g block for $8.29, or $1.66 per 100g, and the Anchor 500g was $9.99, or $2 per 100g.

Woolworths Westgate, just a kilometre away from Costco, was today pricing its store-brand Woolworths Butter 500g at $8.49, or $1.70 per 100g, and Anchor 500g was $9.90, or $1.98 per 100g.

It was no wonder there were reports of Costco’s salted and unsalted varieties running out as shoppers took home trolley-loads of butter.

Loyal customers have shared photographs from inside the store this week, showing lines of people waiting to get their hands on the cheap produce.

Several customers have spoken of their disappointment after travelling some distance to the store specifically for the butter, only to find stocks had sold out.

And today, photographs were posted on the store’s unofficial Facebook page of notices inside the shop about purchase limits.

“Limit 30 blocks of butter per membership (i.e. per household),” the store’s notices said.

However, it seems the restrictions were not enough to keep enough stock on the shelves this morning.

One Costco customer reported the store had run out of salted and unsalted butter at 10.24am, less than half an hour after opening time.

Westpac economist Paul Clark has told the Herald that retail prices for butter generally moved in line with export prices.

“Given that, it is reasonable to suggest that, with Global Dairy Trade auction prices for butter having reached new highs, combined with a generally weaker New Zealand dollar … should see retail prices ratchet higher in coming months.

“It is also important to note that retail price adjustments do tend to lag as inventories decline.”

At the latest Global Dairy Trade auction last month, the price of butter rose 1.5% to an average of US$7679/MT (metric tonne). That compares to an average price of US$6815 ($11,546) on January 7.