If your business is something that is fundamentally not “pushing bytes”, you really, really don’t want to know about routers, firewalls, the OSI layer, SHA256, RAID arrays, all the way to this week’s JS framework. All of that is a big annoyance, and paying AWS to “take care of it” makes sense, even if it comes at a higher price: more often than not, the difference wouldn’t be offset by the time, effort, and risk exposure that you would have to allocate when building your own.
This calculation is different if your business is primarily digital. The gentleman upthread making a game, for example, is perfectly right: his company naturally developed a culture that can evaluate and manage every aspect of its digital operations, because it’s part of its core business, so it makes sense to put that knowledge to good use and save money.