Depends on scale of course. There will always be some company that isn't of sufficient size to make it worth the cost.
This is how we actually end up having centralized services. The larger companies who have all this infrastructure, and have the size to justify building their own.. well they inevitably ask themselves "Hey! we have all this infra, we have to pay these people anyways, why aren't we selling excess capacity?"
Then you get AWS. Then as time progresses people at even large institutions that could benefit from running their own infra just go and use another company's infra. Where the other company has evolved into being an infra provider instead of a car parts store, book store(amazon), or search engine.
To answer your question directly. Yes I think this can be done within one engineer salary even if I'm including my own salary. There would be a startup cost that eats into that salary in year 1. But it would be manageable. And then iterative upgrades/replacement parts would be a negligible cost ongoing after year 1. With some financial tricks that startup cost can be spread out over a long enough period that it wouldn't even impact year 1.
I believe he is comparing aws bills vs. engineer time+other hosting bills.