AWS employee here, so I am obviously cloud provider biased, but in my viewpoint having that discipline only comes from having very good, expensive engineers. It's hard to get people who really know how to run a datacenter well, especially when most of the good ones would probably prefer to work for a larger cloud provider since than is more interesting and impactful than running a smaller datacenter for a single company.
The forgotten / underestimated cost is the salaries of these people to set things up well in the first place, be on call to fix things when they break, and perform those upgrades in the same way that cloud providers do.
A single engineer salary can get you a LOT of cloud compute power on AWS. If a cloud provider allows you to build the same thing with two fewer engineers then that's probably an extra $400k or so for the infrastructure budget after you factor in these engineer's salaries, taxes, benefits, etc. And $400k can get you an incredible amount of AWS cloud compute.