This is an interesting post on Passive Voice (original post by Brian DeFiore--awesomely titled "E-Books and Profitability: What We've Always Said and Publishers Have Always Denied"--here). It's a breakdown of how much HarperCollins makes off of hardcovers vs. e-books, and it includes how much the author gets.

The bottom line? HarperCollins does way better, and writers get royally screwed. Quoth DeFiore:

Look at Harper’s own numbers:

$27.99 hardcover generates $5.67 profit to publisher and $4.20 royalty to author

$14.99 agency priced e-book generates $7.87 profit to publisher and $2.62 royalty to author.

I will point out that I make more than $2.62 every time I sell an e-book copy of Trust. Just saying.