Answer: There is no limit to pathetic business practices…
The price of e-books should be the same as their paper counterparts, minus the cost of printing paper and distributing it to you. There is a very slight overhead related to the infrastructure required to digitally store and deliver files. Still, there is no way it costs anywhere near the same as producing and printing paper and moving the results worldwide. As a result, publishers, authors, and sellers should get the same profit margins.
Period. There is nothing else to figure out.
In the real world, weird things happen regarding e-book prices. For example, e-book prices are usually about the same as a paperback but less than a hardcover. This is, in every single case, unjustifiable. The lunacy is turned to eleven when you find e-books much more expensive than their paper counterparts. Example used in article illustration: https://amzn.to/3GVpHLs
On occasion, I am sure you can buy e-books for less than bookstore prices. If you have the patience to look around and follow the various sporadic deals. I have been buying e-book bundles on https://www.humblebundle.com/books for ridiculous prices. If one of the books in the bundle interests me, buying a pack of dozens of books is cheaper than getting that single book for its usual cover price.
It does not make up for the mess the book industry is in.
E-books are convenient. Storing books electronically and accessing them from any device is a life savior, especially for reference material and technical resources. Try cutting and pasting examples from a paper version. My vacation and business travel bags got a whole lot lighter when I stopped carrying around books.
I sometimes enjoy turning to dead tree versions printed on paper and ink when reading longer formats. I may be weird. I know. Yet, according to Pew Research Center research on book consumption and book formats, traditional print remains the most popular reading format for adults and children. So, I am not alone. In fact, I am with the majority.
There is a market for both electronic and paper books. Consumers want to be treated with respect, not being ripped off by an industry lost and confused amid the changes and evolution technology brought along. Get a grip. We have been dealing with these changes for a few decades now. Time to settle down and start acting respectfully towards consumers.