Is it worth publishing a book that doesn't get attention?

So I was just thinking about the books selling in drugstores or the HUGE barnes and nobles book stores… And like, not all of the books get checked out. Some of those books in there I bet my life that people don't even know exist.

First off, not the greatest title question, I know every book has its readers… But still. Won't you actually be loosing money instead of gaining it? I mean, JK Rowling had billions and Susan Collins must be crazy rich too. But thats because their stories are like #1 popular in the world! What about the books that barely anybody knows? Doesn't it cost a lot of money to keep publishing them? Am I just being a jerk? How does it work?
Or… How hard is it to publish a book? I mean, I've seen some bad BAD stories and horrible editing. How hard is it to get your story published?
(Sorry if this sounds totally cruel, I was just curious. I mean, I like to write, so for future reference I guess) Thanks!

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