[onyx]

Fake CostCo ID cards? Hard to believe since the computer at check-out would have registered not-a-valid-account. The Arabs could not have paid in cash (exceeds the 10K limit) and a cheque would have to match the CostCo ID card's account, since all banking account cheques must be on record prior to purchase.

[spycatcher]

Maybe there was more to the story. Got the fake ID and cash info from snopes.com

[poindexter]

For about a year now, Costco membership cards are also American Express credit cards.
You can put your purchases right on the card.