One gram Pamp Suisse gold bars from Costco
Gold has been traded for thousands of years, but it's not really considered currency in the modern sense.
  • Costco sells millions of dollars of gold bars a month.
  • While the bars get snapped up quickly, shoppers are learning that buying is easier than reselling.
  • Trading commodities, as it turns out, is full of complications.

Whenever Costco releases a batch of gold bars for sale, the supply sells out "within a few hours" as shoppers snap up the precious metal for a small markup over its spot price.