That's something I have been asked by various interested peeps when I talk about writing. I haven't made a ton; I know other writers that have made 10x (or more) than me by selling their short stories. The reactions I get when I tell people are usually polite nods, since it would be considered mild pocket change by most standards.
I don't really write to make money, though that would be the dream (stay at home and write versus have a grown-up job). It's more to cleanse my thoughts of the all stray voltage – and frankly, as I get older, it's good to keep my brain engaged and focused. I look at the pay as a bonus. If I get paid $25 and a copy of the anthology my work appears in (which has happened), my take on that is, "Someone gave me a free book and paid me $25 to read it."
Still, it something worth discussing. Here a post with some interesting information from fantasy authors Paul S. Kemp and Michael J. Sullivan. The Reddit discussion linked at the bottom of the post has some interesting conversation (and for Reddit, is strangely low on swearing and doofus-ry).