Prisma (and Prisma Migrate) can be self hosted, so no corporate boundaries needs to be crossed.
They can run on the same host as your application, so the only overhead is on the loopback interface (localhost).
The SaaS solutions for a young business who does not have the time/skill/resources to deploy/maintain the infrastructure are great.
You should always consider the pros/cons before choosing between a managed or self-hosted solution. And once you scale, you can always go for the self-hosted solution.
Just to clarify: Prisma is an open-source ORM [1] that's available via an npm package, so there really isn't a component that needs to be "hosted" here. (You might be referring to Prisma 1 which came with its own DB proxy server that was run via Docker, but Prisma 2 [2] doesn't have this Docker container any more and is "just" an npm library).
[1] https://github.com/prisma/prisma
[2] https://www.prisma.io/blog/announcing-prisma-2-n0v98rzc8br1
I loved Prisma 1, and probably would love Prisma 2 too, but Hasura was enabling us to query already existing databases without rewriting the schema (and having to maintain it), which was a necessity at the time.
Prisma Migrate is entirely open source and works via a CLI. My understanding of "X as a service" typically includes some web service layer which is why I have a hard time following what you mean with your comment exactly.