For years, Whole Foods has shrugged off criticism that it should be renamed "Whole Paycheck" because it is so expensive. But its high-priced reputation might finally be starting to hurt it. The grocery chain's competitors are luring shoppers away with lower prices, threatening to unlock its long stranglehold on the market for organic food, according to a new note by analysts at Wolfe Research, a New York investment research firm. Recently, stores ranging from Kroger to Walmart to Sprouts have undercut Whole Foods by bulking up their own, lower-priced healthy offerings. In its latest quarter, Whole Foods reported that sales at stores open at least a year -- a key retail metric known as "same-store sales" -- rose 3.9 percent.