With so many retailing giants such as J.C. Penney (NYSE: JCP ) , Sears, and Best Buy (NYSE: BBY ) falling by the wayside in what has aptly been named the "Big Box Apocalypse," it's very reassuring to see Costco (NASDAQ: COST ) , the leading warehouse retailer in the U.S., thriving in the midst of all the retail industry snafu. Costco is still posting healthy gains even as the once mighty Wal-Mart and Target struggle to remain afloat. So what makes Costco tick?