Amazon KDP Printing Costs Changing
This is taken from the Amazon KDP website, you should see it at the top of your bookshelf:
Printing costs will change on June 20, 2023
While not required, you may choose to update your list prices to avoid a change in royalties. You can update your list prices at any time individually on the Pricing tab or, until June 19, 2023, you can run a one-time bulk list price update on your live paperback and hardcover list prices to continue earning the same royalties after printing costs change. Learn about printing cost changes.
