Or so says http://zenith-consulting.com/intro/research/level2.html (which just has a short summary, but links to a PDF report. Claims that Wal-Mart is more about creating the perception of low-prices. (That's higher prices than competitors on 80% of items, not prices which are 80% higher.)

Expectation shift. By trumpeting "low prices", Wal-Mart makes price more important to consumers than it initially was. Wal-Mart features low-priced items at the entrance, and in aisle end-caps, even if the bulk of the aisle contents are standard prices.

Going by the charts, Target deserves to be the market leader for discount stores. No, really, it beats the competition on all fronts, except Wal-Mart for meeting price and scope expectations, and the report claims the price thing is a fraud. Avg. grocery chain ties Target for pleasing vendors and workers. Of course, I usually go to a grocery store for things not sold at a Target.

Wal-Mart genuinely has broader scope of items, so there's a lure of "some prices are visibly lower", "everything I need is here", "all the prices should be lower", "even if they aren't, I'm already here"