Twenty years ago, Amazon was a cheap discount bookseller. Because online offered low overhead, they under priced traditional retailers and dominated the market. Then they forgot about books, and reinvented themselves as the retailers of everything, the E-Bay alternative, the rocket boys, the giant computer timeshare service bureau, the grocery store, and a bunch of other stuff. None of which they do particularly well. Nor are they any longer particularly cheap. Their main stock in trade is logistics. By dominating transportation and delivery market share, they dominate all markets which depend on transportation, which is to say all markets. Like Standard Oil in the 1890's, it's not about the price of the goods, it's the way they manipulate shipping cost. Why it's tolerated I couldn't tell you.

Their prices are routinely 10-20% higher than the shop-around competition, and worse, the price may vary based on customer profile. It's really astonishing that they have so many ardent defenders.