American Express lost 10% of its card business when they lost the Costco deal. Here’s an inside account of how American Express lost the business. As costly as it was for American Express to lose Costco, it would have been more costly to retain Costco.
Costco’s switch to Visa though was delayed. This is a complicated transition for the merchant and for the banks, especially with Citibank picking up American Express’ “back book” (Citibank bought the existing card accounts from Amex).
Now we have a timeline, and what happens next.