I agree with the author's point about using popular tech stacks to alleviate the ramp-up time for new hire productivity, but that is not the optimal solution. The optimal solution is for management to not let high-productivity talent from leaving - increase their comp to whatever offers they might get in the open market. That's how labor economic works - it's a market. Investment bank and management consulting figure…
Not all companies need $500k engineers or can afford them. An optimization at Netflix that improves performance by 1% may save them millions of dollars. The same optimization at a medium-size company may only save them a few thousand. Also, it's much more difficult to quantify the impact of a software engineer compared to investment bankers and consultants. The latter two are directly making money for the firm.
I’d personally disagree with the cost effectiveness argument though. Unless your engineering work really cannot benefit from more skill (and as often as I’ve heard management think their work is relatively simple, in practice I’ve rarely seen it) then you’d have to replace a highly skilled engineer with a small team that would likely cost more than $500k. Packing your engineering firepower into as few bodies as possible is a highly cost efficient strategy, as most of the successful techs know.
On the other hand, a small team is less vulnerable to getting hit by a bus or hired out.