>the publishers are both charging more for digital (despite their costs being lower)

The costs associated with printing and distributing a physical book are a much smaller slice of the pie than a lot of people assume. (Back when I looked into this, it was about $2.50 per copy for a hardback as I recall. The author cost for a PoD trade paperback from Amazon is about $5.)

Also, in general, the end-user price for books is generally significantly lower than it used to be. Go back a couple decades and you mostly paid list price for books and paperbacks usually weren't available for a year or so after a book came out in hardcover.