I found GitHub copilot an interesting heuristic on how expressive the programming language / framework you are using is.
It is very useful for things that I would call boilerplate, e.g. you have almost duplicated code (say in a view and a controller) and need to copy from one to the other.
It is annoyingly bad for autocompleting an api as it tends to be slightly (and plausibly) wrong.
I haven't found it very useful for anything else.
Working on a project where I have to do lots of the first makes me sad, so I tend to try to avoid those projects - but if I was forced to for some reason it would be worth $10 a month. However, if enough of the programming I did could be helped by github copilot for it to be worth that much I would start to get worried I was working on the wrong sort of problems and try to move into something different.