This really would have been better as an addendum to my last blog post on my writing and "the long tail," but it was late and I needed to go to bed. I looked over my sales figures for the last few years and saw that the principle of The Long Tail applies to my short-story collection Flashing Steel, Flashing Fire.
When I published Flashing Steel, Flashing Fire in July 2014, I sold 21 copies that month. Over the next five months, I sold eight copies at a rate of zero (August) to three (September) per month. That's over one-third of the premiere month's numbers in five months. In 2015, I sold 14 copies at a rate of zero (three separate months) to four (February) per month. No sales in 2016 so far, but when you combine the non-premiere months of 2014 with all of 2015, the "tail" has already exceeded the "head." And there's still most of 2016 left.
So if you've self-published anything and your numbers have crashed after the first month or two, don't worry. One or two sales per month over the course of years will add up in the long run.
Of course, if you plan on making a living--or at least more than, as Marko Kloos put it, "beer money"--doing this, you'll need to have a lot of product. One book earning $10 in royalties per month is $120 per year, but ten books earning $10 per month is $1,200 per year. And with that many books available, odds are you'll be earning more than $10 per month in royalties anyway. People who buy one book from an author are likely to buy other books, after all. My story "Ubermensch" is a superhero story, but people who bought it also bought Flashing Steel, Flashing Fire despite the complete lack of superhero stories in it. Moving outside of my own work, people who've bought my friend James R. Tuck's supernatural Robin Hood story Mark of the Black Arrow also bought his hollow-earth blaxploitation story Champion of Hollow Earth.
So as my friend Jeff Baker put it (and he learned the phrase from somebody at LibertyCon a couple years ago), if you want to make bank, "churn and burn."