How much you can make on poker per month depends on a lot of things. One of the main things I would say is how much can you play per month? Maybe you have the time to play 160 hours per month or more, well then you can make more money than someone who can only play 10 hours per month.
That’s one factor.
Another one is which limit are you playing now? If you’re playing on NL2 now, you probably won’t make as much as if you were playing NL25.