Study Says Whole Foods Is Most Expensive Grocery Store According to a new study, Whole Foods is the most expensive grocery store chain in the United States. The study, done by Bank of America and Merrill Lynch, was conducted by gathering info from ten studies in eight different markets for a year. If you’re wondering which grocery store chain is the least expensive, it’s Walmart. Where’s your favorite place to go grocery shopping? What are the things you look for in a grocery store that’ll make you come back?