I fully understand serverless billing, which is why I told you its advantage: scaling to 0 for functions you almost never use. But if you are running literally ANYTHING else, you can get that advantage yourself: run your "serverless microservice" as a *library* inside its caller. You don't need the overhead of an RPC to enforce separation of concerns.

A small startup can pay $5/month to run a monolith on a tiny server commensurate with its use. It can scale that monolith up with use, from a $5 VM offering 1 core and a tiny bit of RAM all the way to a two-socket server VM offering 110+ cores and 512 GB of RAM. Alternatively, a large company can scale nearly infinitely with horizontal scaling. When I worked on a service with a trillion QPS and 50% usage swings at a mega-Corp, that's what we did. All our customers, even the ones with a measly 1 million QPS did the same. And their customers, and their customers, and so on.

"Serverless" was something sold to fashionable tech startups and non-technical people who didn't have the expertise to maintain the VMs/containers they needed. The serverless systems carried a huge price premium too. Everyone with true scale understood that there are servers there, and you are going to pay to manage them whether you want to or not.