If they compete solely upon price profits for dealers will fall. At the same time their costs will remain the same. In the short term a few consumers will benefit, but in the longer term the number of dealers will decline because of low profits and in the end state it is possible that only one dealer will survive. Do you really want to buy high end audio from Amazon? There will be no service, no advice, no system matching, no demos, no trade ins, just a good price. But wait, they're a monopolistic seller, they don't even have to give the consumer a good price.