I'm about to help transitioning a mobile app to a charity and need the API to be hosted as cheaply as possible. I don't expect it to scale super big, but there has to be some level of scalability. Initial effort can be bigger, what's important are the running costs. Ideally it should be low maintenance, not a lot of development is going to happen on the code base. It's nodejs with postgres.

Right now we're on AWS which is crazy expensive, and I'm thinking about going to vercel but can't really estimate how much it will be with equal performance.