"banned books" has a number of connotations. In common PR culture it refers to books that school districts have censored, but are otherwise generally available for sale .
In this article they are referring to popular books on Amazon that are censored from theocratic or Islamist countries.
If you want to find the real banned books, look for books that are $300+ on Ebay. Those are books that publishers refuse to publish and retailers refuse to sell. I'm not aware of statute banning those books, but they are in a practical sense banned from publication.
I am confused about what subset of books you are referring to. Many expensive books, in the range you mentioned, are collectible editions of books still in print.
There was a big battle over whether Amazon would sell a book about transgender children. For a while, it was banned for a bit but then the company changed its mind.
https://www.intomore.com/culture/amazon-reverses-ban-abigail...
I dont think schools should be censoring books, buying precensored books that have the substance yanked out to prevent offending politicians, nor should they be banning books.
I also get super frustrated at Conde Nast for taking a lot of their old shit out of print, causing it to fetch prices in the hundreds.
If I made a gift of "The Turner Diaries" to your local school library, would you "censor" it?