If it was cheaper large companies would not all have moved to cloud, especially since it costs a very large upfront cost to migrate all that over if you already have a full setup

Netflix used to have one of the best homegrown infrastructure and even they moved everything off to AWS

I've worked at a place that mostly just served videos and had 100M users (no idea what the DAU/MAU was). The AWS bill was ~800k a year

Just buying the land and building all the data centers across multiple continents would probably bankrupt the entire company, forget about building all that software and setting up the hardware and configs by themselves

It's only cheaper for tiny companies, but even then, no company ever has the goal of staying small