Upon reading your comment I went to look up Amazon royalty information. Let me know if I got this right.
A book that is 3-10 dollars, sold in the first world, gets you 70% royalties minus a few cents for delivery. If you want to set a price over $10, then you only get 35% royalties.
So it's not that Amazon flat-out gives much lower royalties, it's that they give much lower royalties for books that cost more than ten dollars. They don't want to give you more than seven dollars per sale.
That's basically all true, except it's not always just "a few cents" for delivery, especially if you have full color photos or illustrations as a part of your eBook. On other platforms there is no delivery fee and no price range required to receive the 70% royalty rate. So there is a window for certain books where the Amazon rates are competitive, and of course they have the largest marketplace for eBooks so it's usually advantageous to play within those bounds.
It's ridiculous that to make more money than $7 - download charges from a book you need to go from $10 to $21. This is what Amazon wants -- it wants a bunch of books for less than $10, and it claims that it offers competitive royalties when in fact it doesn't.
A book that is 3-10 dollars, sold in the first world, gets you 70% royalties minus a few cents for delivery. If you want to set a price over $10, then you only get 35% royalties.
So it's not that Amazon flat-out gives much lower royalties, it's that they give much lower royalties for books that cost more than ten dollars. They don't want to give you more than seven dollars per sale.