When it comes to online dominance, low prices are very important. It is as easy as opening a new tab and clicking on another webpage that would be have a cheaper product. The convenience makes it important, since their options are easy to get to. The other benefits Amazon and Walmart offer are also important since they set them apart from competitors.
While Walmart has lower prices, if Amazon has a slightly higher price but offers free 3-day shipping, many customers would choose Amazon for the added benefits. When price does not set a company apart, the services they offer will.