Intrigued by how Costco is discovering the many expensive complexities in transitioning from store-branded card to another.

Costco has said that it needs more time than originally announced to make its move from Amex to Citigroup Visas. It had initially announced an April 1 cutoff date but the retailer now says it will be closer to “the middle of summer,” according to a well-done piece in Lowcards.com. The story quotes Costco CFO Richard Galanti characterizing the transition date as “fluid” and saying “It’s between Amex and Citi–negotiating and completing the agreements to do that transition.”

And while this is going on, Costco is doing without the finder’s fee that they had been getting from Amex. On top of that, the longer the delay, the more time that goes with Costco paying the higher Amex interchange.

As any divorcee knows, wrapping up any 16-year relationship tends to be really costly.