Average markup on e-textbooks (e-books in general will due, if cannot
find specifically e-textbooks). Generally e-books are sold directly
from the publisher so markup is purely over cost. However, there are a
few retailers, and I am wondering what they are paying to get the
e-book licenses to resell, and how much they are marking them up from
there? Examples include: Blish.com, ereader.com, and ebooks.com. I
have found that e-books are priced (retail) at 50% of the hardcover
equivalent. So, do e-book retailers acquire the licenses for less than
50% of the hardcover equivalent and then markup to the 50% price tag,
or are only e-books directly from the publisher priced at 50% of the
hardcover equivalent, and then retailers mark their sale of the same
e-book up more than that? (I am moer concerned with e-textbooks,
however if e-books result extends also to e-textbooks, then great).

I can answer this (I worked at a publisher setting up their eBook
campaign from 2000 - 2004 and now I'm a consultant in that area) but
I'm not signed up as a researcher and Google aren't accepting more
applications at the moment. Basically, the publishers sign a deal with
each retailer. That deal sets how much freedom the retailer has to
price the ebooks - generally not much, and often publishers price to
match the print copy of the book - the HB version if it's an academic
book, or sometimes at parity with the PB if it's a trade title.

The publisher send the eBook files to the retailer for free, and the
retailer only send royalties back to the publisher when it gets a
sale. Discounts tend to be around 35-40 per cent. The trade market
(eBooks.com and the others you refer to) have not seen big sales yet.
The academic market (ebrary.com, Netlibrary.com) have seen big sales
and these sales models are therefore a bit more advanced. The
purchasing power of library consortia has also meant the model has
evolved somewhat in the last few years. Get in touch to discuss more
if you like (for free, this isn't for the money!!) Best wishes  Dan