Amazon's stated goal is to have no margins (Bezos 'your margin is my opportunity'). So yes if they are following their zero margin strategy they should be lower than WMT, whose only claim is low price. If something is cheaper elsewhere it is because Amazon has not figured out how to deliver that particular item to the consumer at cost yet. So for example if you find something cheaper at WMT it may be that WMT has a great distributor license and is an exclusive channel, something like that.