Print houses are increasingly using the same source and layout files for printed books as they are for ebooks. This means that there is little to no difference or extra cost to produce the alternate media version here.
I totally agree that an audio book has an entirely different production path and it's own entirely different staff and company that needs to make it's own costs back. But that argument is becoming less and less relevant for physical vs digital books.
Many non-traditional/smaller publishers and printers, such as No Starch Press, offer free copies of the ebook version when you purchase the physical copy and offer the digital copy at a reduce price compared to print.
I totally agree that an audio book has an entirely different production path and it's own entirely different staff and company that needs to make it's own costs back. But that argument is becoming less and less relevant for physical vs digital books.
Many non-traditional/smaller publishers and printers, such as No Starch Press, offer free copies of the ebook version when you purchase the physical copy and offer the digital copy at a reduce price compared to print.