It is reported that Costco, the world's largest chain membership warehouse, sells a variety of goods, including rbob gasoline, hot dogs, gold bars, and more. However, according to CEO Ron Vachris, the company's most important product sold is its membership, not the items on the shelves.

It is known that Costco has 130 million memberships, with members paying annual fees of $60 to $120. Cheaper memberships allow members to shop at all Costco chain warehouses, while more expensive memberships also offer members an additional reward of 2% cash back on each purchase.

Since 2016, Costco's membership has grown by 50%, with membership fee revenue reaching $4.6 billion last year. More importantly, Costco's members are very loyal. According to Costco's recent annual report, 90% of cardholders choose to renew their membership.

Since only members can shop in Costco's warehouse, the supermarket is designed to attract them back, from the affordable rbob gasoline station to Costco's famous rotisserie chicken, Costco wants members to feel that they get a good value.