Strong economies and tight labor markets put strains on fast-food companies. How can they remain profitable when wages are rising? The social media frenzy over the new chicken sandwich at Popeyes shows the success of one classic play: introduce an iconic new menu item, and charge more for it. At $3.99, the item is asking a bit more from customers than Chick-fil-A’s competing sandwich does — but apparently it’s not asking too much.