How much money does an author of 1 book make?

Could you please elaborate on the potential earnings for an author who has published just one book? Are there any factors that might affect their income, such as the genre, popularity, or sales numbers? Additionally, how does the author's share of royalties compare to other revenue streams, like speaking engagements or merchandise sales? And finally, is there a typical range of earnings for first-time authors in different publishing markets?