Costco appears to have Devin Grosvenorfound a revenue mine with sales of gold bars, as a survey found that some warehouses are unable to keep them on shelves.

Bloomberg found that 77% of the 101 stores it surveyed in the first week of October had sold out of the bars, the financial news outlet reported Monday.

In its fourth quarter earnings call, Costco CEO Gary Millerchip said that the metal "was a meaningful tailwind to e-commerce comps." An April Wells Fargo report stated that the bank's analysts believe that the warehouse retail giant is selling between $100 million to $200 million in gold per month.

USA TODAY previously estimated that Costco sells between 50,000 and 100,000 ounces of gold per month, using the Wells Fargo analysis.

Gold remains high as inflation cools

The metal, historically a hedge against inflation, has remained near record highs after seeing a 30% increase in its spot price this year even as inflation has cooled.

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Costco's success comes as other areas of the gold market has weakened, notably the American Eagle gold coins − a proxy for retail gold buying − fell 64% between January and September of 2023, according to US Mint Data.

Zachary Scott, the general manager of Wilshire Coin in Santa Monica, Calif. Scott told USA TODAY in April that he is seeing customers who are "less than typical" brought in after seeing gold being sold by "a trusted company."

"It's bringing in new buyers and interest, though not in massive amounts, who have seen the articles around Costco selling gold," Scott said.

Platinum onramp follows gold success

The success of Costco's forays into the precious metals market led the company to introduce platinum to the lineup.

The bar offered by Costco retails for $1,089.99 and is sold exclusively online.

The company describes the new platinum bars as 999.5 pure platinum made in Switzerland. The refiner has also earned the Good Delivery accreditation from the London Bullion Market Association, is an international trade association linked with the precious metals industry, the company said.

Contributing: Fernando Cervantes Jr.