It doesn’t sound like OP was optimizing anything; it sounds like they just knew how to use that stack, and so are able to get customer validation while also spending very little per month.
Fair point. Stack selection is mostly about what you already know. I chose managed services not because I optimized for it, but because that's the stack I'm comfortable with.
That said, my real point was simpler: whatever stack you pick, figure out who's going to pay for it before you spend time on infrastructure decisions.