When publishing e-books on Amazon, file size is an important consideration.
First of all, Amazon charges delivery fees for any books priced $2.99-$9.99 if you've chosen the 70% royalty rate (and even with delivery costs, you generally want to choose the 70% rate). They calculate your royalty and then subtract the delivery cost, so a big delivery cost can really eat into your profit margin.
Delivery cost depends on file size. If you're publishing novels or narrative non-fiction without fancy graphics, it's probably not a big problem. My books of this type have delivery costs of 3-6 cents. If you're publishing something with photos, illustrations, charts, etc, then you have more to worry about. My book, Cruising Alaska on a Budget, could easily have had delivery costs above 70 cents, even without putting in all the photos I wanted. I got it down to 22 cents through photo editing and somewhat complicated computer gymnastics. I'll detail my process in another post, but that scaling down left me a lot higher percentage of profit.
Even if you choose the 35% royalty rate (or take the mandatory 35% rate for books $0.99-$2.99), you still have to think about file size.
If you want to price your book at 99 cents, your converted file size must be under 3 MB. My current book, Hiking Alaska from Cruise Ports, is a relatively short book, and it's only 99 cents for its launch. The file I'd prepared, however, full of pictures of the beautiful trails and stunning views, was bigger than 3 MB. Despite my publishing experience with KDP, I'd never run into this problem before, and it took me some Googling to figure out why I couldn't price it at 99 cents, so I thought I'd share it with you all.
For more detail, you can read my post on Have Book, Will Travel.
Keep an eye out for my personal file-scaling-down method next time.
Melinda Brasher's fiction appears most recently in Leading Edge (Volume 73) and Deep Magic (Spring 2019). Her newest non-fiction book, Hiking Alaska from Cruise Ports is available for pre-order on Amazon.
She loves hiking and taking photographs of nature's small miracles.
Visit her online at http://www.melindabrasher.com