It's not the electrons in the ebook, or the paper and glue in the printed book, that you are paying for. It's the intellectual property. I need 2 to 3 years to write 250,000 words of deathless prose in the form of epic novels.
My 560-page dead-tree books cost very little of the retail price to produce. You might as well ask why I charge $20 for a "three-dollar book."
You are paying for the two or three years of my life, spent in a tiny writing closet, to produce that novel.
Oh I agree. But the question is why does an e book cost more than a dead tree book?
The other problem is similar to why most pilots are paid very poorly. People dream of being an author, and with lower barriers to entry, prices will go down.