I don't think I have joined a startup that pays less than 20k/month to AWS or any cloud in almost a decade.
Biggest recent ones were ~200k and ~100k that we managed to lower to ~80k with a couple months of work (but it went back up again after I left).
I fondly remember lowering our Heroku bill from 5k to 2k back in 2016 after a day of work. Management was ecstatic.
Doubt it. I've personally seen AWS bills in the tens of thousands, he's probably not that costly for a day.