Why are tens of millions of upscale buyers paying just to walk into a stripped down warehouse store?
That's the story behind Costco, the nation's second largest retailer and the world's leading warehouse membership chain.
In the new CNBC original documentary, "The Costco Craze," Carl Quintanilla examines how this store has built a $93-billion empire.
It's estimated that 64-million people have joined the Costco craze.
Everything in the stripped down warehouses is sold in bulk. There are no signs to help direct customers inside.
Costco says it wants customers to explore the store and hopefully come across additional items that maybe they weren't expecting.
Many shoppers admit they come out of the store spending more than they intended.
Here's how warehouse membership fees and prices stack up.
Costco's basic membership is $55 and their prices are about 30 percent lower than the largest supermarket chains.
B-J's membership costs $50 and prices 29 percent lower.
Sam's Club is $40 and prices are 33 percent lower.
Some experts say membership fees actually cause people to spend more because they think they need to earn back the fee they paid.