For an ebook, it's hard to say. Several years ago when I re-issued some of my own books $2.99 was considered about right. But prices have gone up a lot since then. Now prices are all over the place. I would say that 7 or 8 dollars is perhaps the average.
But it depends. As a first novel, and self published, you might want to be fairly conservative in pricing your book (as I see, by the first post in this thread, that you have). If you go too low, people might think it's a sign that the book isn't very good. Too high and they will think it's over-priced. I bought an ebook of a short story by a new-to-me writer,that was thirteen or fourteen dollars, which I did think was outrageous, but I was really attracted by the book description, and the writer, though comparatively new, was highly regarded (I think this was what decided me), so I gritted my teeth and bought it. But normally I would never pay nearly so much for anything less than novel-length and by a writer I already particularly liked. In this case, I liked the story and the way it was written sufficiently well that I don't feel ripped-off—I mean the book wasn't misrepresented, and I enjoyed it, so at least there was that—however, I don't see myself repeating that experience, whereas had the price (and the prices of subsequent stories) been more reasonable I would almost certainly have gone on buying her books. For whatever such anecdotal evidence is worth.
But there are other factors to take into consideration. Is this book a one-off, or do you have more in at the same series or at least of the same sort, to be published in the near future? Then you might want to price it very low (or free) to attract readers now and charge more for subsequent books once you have readers eager to read what you publish next. I have seen a lot of writers price the first book as free or perhaps 99¢, then the next book costs a few dollars, the next even more, and then further books at about the same price as the third book, depending on length. I do not know how successful this is as a strategy. Would so many writers be doing this if it didn't work? Maybe, maybe not. I can say as a reader that it has sometimes hooked me on a writer's works.
