Plus they bully their suppliers into submission by offering them such immense distribution deals that would help get their name out, but they are then forced to drop their prices to whatever Wal Mart dictates. They get more exposure but lose money. It's a "damned if you do; damned if you don't" situation. For example, Vlassic pickles was about to go under recently. So they sought out Wal Mart to help them out. Wal Mart forced them to start packaging their pickles in big gallon jugs instead of the traditional smaller jars that Vlassic always sold them in. Wal Mart would then sell these jugs for $2.99 each. When all was said and done, Vlassic made only 3 cents per jar of pickles sold. Some deal, eh?
Wal Mart has killed the old style of doing business in the US. So many thousands of mom-and-pop and specialty stores have closed their doors because they just cannot compete with Wal Mart. I have several friends who either have closed their stores or are about to because of Wal Marts coming into their areas and just killing them.
Read any marketing book for examples of why Wal Mart is both genius and tyrant in the business world. Don't just assume that low prices are better.