Costco runs membership warehouses that sell a deliberately limited selection of goods in bulk at thin markups. The real profit engine is the annual membership fee, which renews at rates above ninety percent in North America and turns shoppers into a recurring revenue stream. The Kirkland Signature private label commands loyalty that rivals national brands. Costco grows patiently, opening a modest number of warehouses each year across the US and abroad, and its low-price reputation is guarded as the company's most valuable asset.