Costco Sale: Zippy Sack Twin 3-Piece Set $16.99 by Rhonda July 16, 2020 12/28/16. Blankets always ending up on the floor? Costco has the Zippy Sack Twin 3-Piece Set on sale for $16.99 (after manufacturer’s instant rebate), now through January 3, 2017. That is … 0 FacebookTwitterPinterestEmail