What percentage in royalties does an author usually get?

Answer 1

I don't know how reliable this is, but here's a quote from the article linked below:

Generally speaking, hardcover books pay standard royalty rates of 10%, 12%, and 15% of the cover price --- 10% on the first 1 to 250,000 copies sold, 12% on the next 250,001 to 500,000 copies sold, and 15% on anything sold above 500,000 copies. So if an author's hardcover book has a cover price of $25.00, then the author will earn only a $2.50 royalty on every copy sold, up to 250,000 copies.