[If you want to see just how successful hard work and a solid promo plan (along with good books) can be, check out some of the posts Patty Jansen does on her far more active writing career.]
Earnings per monthFirst, here's earnings from when I first put my books up on Amazon (a few months after I'd first published them on Smashwords). The two big peaks are two Bookbub promotions, back when it was easier to get into Bookbub. The initial early leaps were in the days when putting a book free would have a tangible impact on your sales. [The third biggest peak, incidentally, is the release of In Arcadia.]
Earnings by book and storeThe Touchstone Trilogy is by leaps and bounds my bestseller, as can be seen by the pie chart. No prizes for guessing which books are represented by the right of the chart.
Numbers and dollars by book
Dividing this by seven years makes the amounts seem much less impressive - but still definitely nothing to sniff at! Not anything I could gamble on early retirement with, but a solid supplement to my income. [Publishing and Amazon algorithms are such variable things that I don't think I would ever bank on book royalties until I no longer had things like mortgages to worry about.]
For the future...well, I'd still rather just write and publish and see what happens - the beauty of self-publishing is that the books are mine, and they're not going away, and I'm comfortable with letting my mailing list grow slowly and organically.
Not that I'd object to wild success. I recently had a rather heart-stopping query from a very major production company about the film/TV rights for Touchstone. It came to nothing, sadly, but it sure did give me some fun daydreams. I re-read the trilogy afterwards, and really don't see how it could be adapted without cutting down on the massive cast list - but I thought it would be fun to have a show that paralleled Zan and Cass. They both technically 'graduate' around the same time and are such different people.