For my books...
I publish a few books, and also make them available as EBooks (using Adobe DRM).
I set the prices for the eBooks at the level to give the same commission on a sale to myself; since there is no printing cost this means it is about 2/3 the price (there are still publishing and retailer fees, etc). There is also a $2/book license fee for the Adobe DRM to include in the cost.
If I was selling via Amazon, then the retailer's fees are massively higher; in fact, the actual printing costs on a $15 book are less than $5. All the rest is the publishers cut, the retailers cut, and so on... so it sort of makes sense that eBooks are only slightly cheaper than dead-tree versions. Still, making eBooks MORE expensive than dead-tree makes no sense at all, unless you're trying to screw the buyer...