What I've noticed with "upscale" stores like Whole Foods is that their "experience" is just totally different from WalMart (others have pointed this out in other threads).

For people beyond a certain income level, a few dollars in savings aren't as attractive as shopping in a place where people seem to be more "happy". Many of these stores also tend to have an attached gourmet cafe where you can grab a "healthy" bite post/pre shopping. The whole foods in Downtown Austin even has yoga classes (an other fitness activities) on its terrace.