What are the chances of a writer actually becoming successful?

I don't mean bestselling author, Colleen Hoover (gags), Rick Riordon, J. K. Rowling type successful. I just mean a, like, sustainable amount of people actually buying your books, if that makes sense?

I know a lot of things factor into that: having social media to promote your writing, getting traditionally published, etc etc. But still; I'm curious.

edit: I'm not asking because I wanna be big and successful; I'm more than happy with just a few people buying my book(s). I'm just genuinely curious LMAO