BookBub produces some excellent and informative information on ebook prices as related to sale/promotion pricing. Kudos to them for sharing this info. (As opposed to the 700-pound gorilla not to be named, who shares no info at all.)
7 Top Ebook Price Promotion Stats You Need To Know
If you are a self-pubbed author and setting your own prices, do read this whole article. Two points of interest — It’s not just low price that drives sales. If your author name or book title are already well-known, you can make more money by not going too low on sale pricing — go to $2.99, not $0.99. And keep sales to five days or fewer in order to increase post-promotion revenue.