Serious question: Why is it that everyone believes that going to the cloud is cheaper? How is it that AWS can buy the same servers, same switches same everyth

Serious question: Why is it that everyone believes that going to the cloud is cheaper? How is it that AWS can buy the same servers, same switches same everything, make a fat profit and somehow it's sell it cheaper than you can do it? I get that there are economies of scale, but not 2-3x right? Sure, you don't need those admins to rack up new servers, but don't you just trade those costs for costs around AWS "devops"? (IAM / authentication anyone?). I keep hearing execs telling me that moving from self-hosted to AWS is going to save a ton of money ... but I just don't believe it. I would assume if you're that bad at running an IT business in-house, you'll be just as bad at it in the cloud.