[eping]

I think this is a temporary phenomenon.
Currently, the fixed/base cost of eBook is more than paper book. They need digitalization, format conversion. Such work is costly for fewer worker can do it.
There is still no good software in epublishing field as Ms Word or Page Maker/indesign in paper publishing to do the work. Some of the work are now performed by human labour.

But this cost can be lowered by the improvement of the technology, such as ePublishing software and the whole industry system.

Some new software like Sigil and ePub Maker can accelerate their speed and lower their cost greatly, but still not noticed by these major publishers.