Costco has added a popular fast food product, Chick-fil-A's Signature Sauce Set, to its shelves. The move aligns with Costco's tradition of rotating products that rotate in and out. The company's strategy is effective as it uses changing inventory and seasonal drops to keep members engaged and return more frequently. During its most recent operating quarter, Costco reported a 14% year-over-year increase in net income and a 7.4% increase in comparable sales. It's unclear whether the Chick-Fil-A Signature Sauce set is a permanent offering or a limited-time offering. The retailer also explains its strategy on its website and encourages members to purchase items that interest them more often.