Currently on GrapheneOS relay works without Google Play Services. eSIM support _does_ require "sandboxed Google Play": https://grapheneos.org/usage#sandboxed-google-play-esim

Much much more discussion on this here: https://github.com/GrapheneOS/os-issue-tracker/issues/159

The $5/month price is for the Relay functionality which provides the 2-hop traffic tunneling. I'm guessing(?) that's not more than your monthly phone bill?

The $90/month price is for unlimited mobile data, so it would in theory replace your phone bill entirely.

There's a lot more info on this thread: https://news.ycombinator.com/item?id=32399347