Hosting yourself makes sense if you're providing hardware level services like storage or compute. In that case, going to the cloud is literally financing your (potential ) competitor.
I worked for a small (~300 headcount) software company that did CFD software. We were told to build out our HPC capacity so that customers could use our hardware to run their jobs instead of having to manage a cluster themselves to run our software. The software was billed per core-hour, and that was the only charge. It made no difference if you ran it on your infrastructure or ours-there was no additional charge for our compute or storage or network bandwidth.
We bought compute in units of between one and four racks fully populated, usually lease with a trivial buyout at the end, or just outright.
In the last 24 months we were an independent company, our SaaS infrastructure drove an additional $24 million to EBITDA. In that increment, we spent $9 million total on hardware, colo, network connectivity and our salaries. The total cost of replicating our compute capacity (for those 24 months) on AWS was ~$31 million. This all came out on the due-diligence that we had to do as we were being bought by a larger firm, so the accountants were satisfied that the numbers were accurate.
IOW, the article seems to be completely plausible.
If you’re a business leader, you‘re probably just blindly following what your peer business leaders are doing, that’s why you’re on AWS (in most cases at least)
What I'm struggling with is their estimate. I work for an enormous enterprise that runs tons of stuff on the cloud and our budget is less than a quarter of their AWS estimate. We avoid products like EBS unless they are necessary, and use RDS whenever possible.