Comment by andai
Without additional context, my guess is that you could have sold more if you had gotten more exposure. If the quality is good and there is a market for it, then it's only potential readers not knowing about it that prevents them from buying it.
I should have mentioned this part indeed. Finding a publisher and following their process is already a hard path. But if you decide to self-publish (which I did) then a whole new story begins. Being a good author is not what matters at this point. You'll need good communication skills and a strategy to get some visibility. You'll need to market your "product" and feel at ease with this. A self-published book can be amazingly written, but without a very good strategy it's a book no one will read, sadly (especially if your audience is very niche, like mine). It's the part I feel the least comfortable with, so I have to accept the very limited reach.