Veteran author Jim C Hines offered some of his titles independently direct through Amazon's Kindle store. He discovered that Amazon reserves the right to arbitrarily reprice his books — slashing the cover price of a $2.99 title to $0.99 — and pay royalties on the lower price.

Hines points out that when his traditional publisher and its bookseller partners decide to offer his work at sale prices, he still gets paid royalties based on the cover price, and discusses the difficulties he faces in lacking the clout of an agent or a major publisher in negotiating with Amazon over this practice.

With my DAW books, if a bookstore offers a sale, I still get my royalties based on the cover price. Amazon is selling Libriomancer for pre-order at almost half-off, but I'll get paid my full amount for every copy sold. Not so with self-published titles. Looking at my reports for last week, my royalties were slashed by 2/3 for every copy sold, because Amazon paid me 70% of the $.99 sale price, not my list price.

According to the KDP Pricing Page, royalties should be based on the list price ($2.99) unless the price adjustment was due to a price-matching situation (dropping the price to match a competitor's price) … but my royalties report still shows a 67% cut.

When I followed up with the DTP team, they responded thusly:

The price at which we sell your book may not be the same as your list price. This may occur, for example, if we sell your book at a lower price to match a third party's price for a digital or physical edition of the book… In this case, if you have chosen the 70% option for your book, your 70% royalty will be calculated based on our price for the book (less delivery costs and taxes).

Of course, this wasn't actually the case, as there was no lower third-party price. I asked them again to show me where their Pricing Page or Terms of Service allow Amazon to arbitrarily cut your book's offer price and reduce your royalties based on that change. I haven't heard back from them.