ebooks are more expensive

Does anyone know why e-books are more expensive than the physical copy? One of the primary reasons for selling an ebook would be that it should cost much less, instead I notice $5-$10 or more premium.

example - powell.com ebook $25
amazon.com physical $20
list - $30

 

Likelihood of sharing?

 

I dont think that fully explains it.
However ADBE trading at around 50% in 52 weeks.