They're less than razor thin. They generally lose money every time they sell you something. This has become less true over time with the explosion of third pa

They're less than razor thin. They generally lose money every time they sell you something. This has become less true over time with the explosion of third party sellers, but it's still generally true. The revenue from Amazon Prime subscriptions does not cover the costs of providing benefits to Amazon Prime subscribers. Costco has a different target market than Amazon. They target relatively well off people who can afford the upfront cost of a membership and have the capital to buy goods in bulk. That customer base places a relatively high value on customer service.