> If the migration took more than one man-year then they lost money.
Your math is incorrect. The savings are per year. The job gets done once.
> Also what happens at hardware end-of-life?
You buy more hardware. A drive should last a few years on average at least.
> Also what happens if they encounter an explosive growth or burst usage event?
Short term, clouds are always available to handle extra compute. It's not a bad idea to use a cloud load-balancing system anyway to handle spam or caching.
But also, you can buy hardware from amazon and get it the next day with Prime.
> And did their current staffing include enough headcount to maintain the physical machines or did they have to hire for that?
I'm sure any team capable of building complex software at scale is capable of running a few servers on prem. I'm sure there's more than a few programmers on most teams that have homelabs they muck around with.
Also what happens at hardware end-of-life?
Also what happens if they encounter an explosive growth or burst usage event?
And did their current staffing include enough headcount to maintain the physical machines or did they have to hire for that?
Etc etc. Cloud is not cheap but if you are honest about TCO then the savings likely are WAY less than they imply in the article.