Because a book being $100 vs $5 on Amazon because someone in a position of power made an ideologically-based decision actually meaningfully affects the ability

Because a book being $100 vs $5 on Amazon because someone in a position of power made an ideologically-based decision actually meaningfully affects the ability of ordinary people to access that book, even though I agree with you that this is not a book ban in the ordinary sense of the term and that legally a copyright holder can choose to cease publication for any reason.