I think you're exactly right. It has become a HN trope that every cost optimization story gets a response like this: your infrastructure costs are trumped by the cost of your developers, so why spend the expensive resource (developers) on optimizing the comparatively cheap bit (infrastructure). I'm tired of the trope because it's such an oversimplification.
What matters is the return on investment, and as you state, one of the great things about cost optimization is that its returns come largely risk free. By my math the optimizations described here return $100k a year. On a risk-adjusted basis, what task could this developer have performed that would have returned more?
In this thread line regarding small businesses, another critical point is that the $24,000 (and certainly in the $100k premise) also might be part of the remainder compensation or profit calculation for the owner of the business. Sure it pales next to the cost of five engineers and yet it could easily be anywhere from 1/10 to 1/3 of the annual profit for a small business. If you're the owner, that's a big deal over time. You never know how tight a small business has to operate, however typically it's thinner than not.
What matters is the return on investment, and as you state, one of the great things about cost optimization is that its returns come largely risk free. By my math the optimizations described here return $100k a year. On a risk-adjusted basis, what task could this developer have performed that would have returned more?