Yahoo Finance analysis indicates that Amazon's forward P/E ratio is currently around 20x, significantly lower than Walmart's 37x and Costco's 44x. The analysis suggests this is primarily due to Amazon's planned massive capital expenditure of $220 billion this year on AI infrastructure, leading investors to be cautious about its yet-to-be-fully-determined market value. Meanwhile, some investors, concerned about a potential collapse in the AI industry, have shifted towards defensive stocks like Walmart and Costco, pushing up their valuations.