Definitely not a random sample, but interesting all the same... http://www.jimchines.com/2017/02/2016-novelist-income-results-1/
In my limited experience, those authors who sell very few copies are far less likely to share that info, even if it's anonymous. That said, making money...decent money or even earning a living isn't impossible. Hard work, being productive, continuing to improve skills, and a little luck, why not?
Income is a very long tailed phenomenon these days. Ordinary statistics will be misleading. But that curve will give the right idea.