First, be aware that delivery fees are based on the size of the file sent to the customer, not the size of the ePub that you upload to Amazon.
The size of the ePub file you download from Atticus is not a reliable means to estimate how much your delivery fees will be. Your Atticus ePub contains the formatting necessary for the eBook to work on many different devices and apps, but only a limited amount of this information will need to be delivered to a customer when they purchase the eBook from Amazon.
After uploading your ePub to KDP, their automated system will convert and optimize the interior to ensure it is Kindle-ready. This will include compressing various elements and eliminating elements that aren’t necessary for the Kindle format. Once this process is complete, you will find your final file size and the delivery fee on the next page of KDP’s dashboard.
What isn't included in Delivery costs?
Font files
Cover Image
What is included in Delivery costs?
Text
Interior Images including chapter header images and scene breaks
Interior images contribute the most to the size of your delivery fee.
When you use the same image for chapter headings or ornamental breaks, Atticus automatically optimizes the eBook output to reference all of these images to a single image file which reduces the overall eBook size.
If you are using different headers for each chapter, the size of your deliverable file will increase.
Atticus automatically compresses and optimizes your images for ePubs, however, this process is limited to preserve image quality.
The most effective way to decrease delivery costs is to:
Use the same image for all chapter headings rather than turning on Individual Images for each chapter.
Exclude large, full-page images from the eBook.
Ensure that all images are sized appropriately for display in eBooks.
Compress and optimize images before uploading to Atticus.