We have a mature TF module library and can roll out complex, well configured infra in a matter of hours, reliably. That said it's platform specific.
Sure, managed service costs are certainly a thing, but to my point that only really start to become an issue at significant scale, assuming you're well configured.
The cost metrics that make "it's cheaper to use managed service than pay the cost of extra engineer to specialize in infrastructure" aren't universal. In fact, I usually have to work from the opposite direction, where hiring a senior Ops specialist who can wrangle everything from shelving the physical hw to network booting k8s cluster on-premises can be cheaper that Heroku/AWS/etc.
Sure, managed service costs are certainly a thing, but to my point that only really start to become an issue at significant scale, assuming you're well configured.