The reason I think parent comment is FUD isn't because I don't acknowledge tradeoffs (they are very real).

It's because parent comment implies that people behind "reclaim the stack" didn't account for the monitoring, people's cost etc.

Obviously any reasonable person making that decision includes it into calculation. Obviously nobody sane throws entire monitoring out of the window for savings.

Accounting for all of these it can be still viable and significantly cheaper to run own infra. Especially if you operate outside of the US and you're able to eat an initial investment.