Whether you wish to add a price to the back cover of your book is totally up to you.
Keep in mind the RRP is only a recommended retail price and each retailer will receive this information as part of our book metadata anyway whether it is actually physically printed on the book or not. As an author it can also be nice to have the flexibility to raise or lower your book price at some point in the future, if you print the price on your cover then you will have no flexibility to do this.
If you decide you want to place an RRP on the cover then we would typically recommend adding this next to the barcode. The booksale currencies are USD, GBP, EUR and AUD so you need to include a price in any/all of these depending on where you intend to sell the book.
It is also possible to actually embed the price of your book into the barcode itself. However, this will be included in USD only so if you intend to sell in other markets then we wouldn’t typically recommend this.
Please let us know if you would like to add prices to your back cover and if so, please provide the prices you would like us to add.