I think this is the problem that should be addressed.
Musicians went through a similar process in reverse order: first Napster ("piracy") then streaming services (analogous to Kindle/Amazon, where a huge 3rd party inserts themselves between content creator & consumer). Eventually some musicians twigged that they were getting screwed every way, so they set up ways for fans to pay them directly or via a less money-hungry intermediary (e.g. Bandcamp).
Not a perfect solution by any means, but if book authors feel their situation is bad enough, they could look into how musicians are dealing with it.
I'm probably not alone in thinking I'd far rather pay an author directly than Amazon or book publishers.
"Bookcamp", anyone?
Personally I have no issue paying for books and other media as it's not the price keeping me away. My issue is that any amount of that money going to providers that are pushing this DRM locked content, which I will absolutely under no circumstances support, no matter how cheap.
Giving money so a good thing you enjoy can continue existing really isn't a concept that's completely out there for most people. There's a thriving ecosystem of platforms for funding/tipping/donating.