The cost of pdfs comes up a lot, remember if you buy the book you get the pdf for free.
Now imagine only the pdf were offered for sale - you would still have
author costs
art costs
layout costs
editing costs
formatting costs
then there are utility bills, employment taxes, corporation taxes and all sorts of overheads.
So the pdf alone needs to cover these costs.
The price to actually print the book is not all that great compared with the above costs. As I often say, the artist must eat too.
What I would like to see is a discount for buying the book if I have already bought the pdf.