I won't publish the ask (they asked me not to), but I thought I'd still answer it publicly!
no, royalties are not a significant source of income for most authors. if you wrote something like Project Hail Mary, then absolutely, the royalties would be substantial! but that's like winning the lottery. Ryan Gosling is not starring in the movie adaption of most books.
when you sell a book to a publisher, you get what's called 'an advance against royalties'. it's usually split into multiple parts, so you might get one third for the initial sale, one third for the final revised manuscript, and one third on the publishing date.
an advance against royalties is the publisher saying "we believe you will eventually make X amount in royalties, so here it is ahead of time." and then you don't actually see any money from royalties until the advance is paid off. most books do not make enough in royalties to pay off the advance (I have two children's books and one fiction book, and have yet to see royalties for any of them).
advances are still great, but you need to make them stretch! for instance, last year my net income was about 30k Canadian (21k USD), which is fantastic when you consider that I mostly made it through writing. but I'm definitely not a millionaire. I can live off my writing (not trying to undersell that!) but I'll probably remain in a low income bracket for the foreseeable future.
this isn't meant to discourage anyone from seeking out writing as a career! however, there is a reason that many authors have alternate jobs with writing on the side. or, you know, rich spouses.
this isn't me making a fuss about pirating (I've pirated way too many shows to run my mouth on that lmao), but there IS actually a financial incentive to having people buy your books!
buying books shows the publisher that they can make money off you, which means they're more likely to give you advances for future books. and advances are what authors live off (if they don't have a side job). that's why I always push pre-orders so hard! you have to be a racehorse worth betting on, or else they send you to the glue factory....
if I can offer one alternative to pirating: asking your library to stock the book also helps authors, and doesn't cost anything. the only downside is the patience required.
OOPS yes, @stjohnstarling makes a good point! everything I'm saying is from the perspective of traditional publishing, but it's a very different game if you're a self-published author
