Maybe in SV the comp is that high. I only have insights into European markets, but here the comp doesn't differ too much from programmers. And an AWS expert won't be cheaper than someone with knowledge how to manage infrastructure.
And yes, you'll need three people, but not full time. From experience I can say that even with a hundred servers, it tends to be a small chunk of each of their time. And if you have a redundant system and don't deploy on Fridays, the chance that someone has to respond to a call on the weekend is pretty much 0.
If you have infra skills then absolutely, it's way simpler to manage. But infra people like don't really fit in "small shops" because the price tag for one of us is (depending on the cost of living) anywhere between a quarter and half a mil total comp. And if you ever want them to take a vacation not on-call you'll need at least three. I say this against my own interest, just go with the managed services and consider it "good problems to have" when you feel the itch to hire some infra person to clean up the debt.