Costco's $60 membership fee inadvertently selects for customers with high income and home storage space, while psychologically committing them to shop more frequently to 'get their money's worth.' The typical Costco member earns $125,000 per year — 70% above the US median — while Walmart's median shopper earns $80,000. Costco has the lowest prices and the wealthiest customers of any major US retailer.