Our cards all came in envelopes. We've bought about 80 cards overall (50 this past weekend) and all came with envelopes. Not that it matters.
Cheers.
You've got good Costco housekeeping. Our Costco doesn't have them in envelopes, so they have to count the envelopes out separately and you get to insert the cards. I like to keep partially used cards in the envelope with the residual value written on the outside.