I purchased several Costco cash cards with a Visa card, and the purchase showed up as an expenditure for purposes of meeting a minimum expenditure requirement. However, purchases at Costco with your cash cards do not qualify for the annual Costco rebate (if you are an Executive Member at Costco), and the initial purchase of the cash card does not earn a rebate either.

As for cash refunds on your Costco cash cards, the cards are printed with a disclaimer that they are not redeemable for cash. In practice, your local Costco store might give you a cash refund as a courtesy, particularly if the card has been largely spent. In my two local Costco stores, one store gave me full refunds for the cash cards, but has recently shown increasing reluctance to do so. The other store has firmly refused to pay any cash on the card.