This idea that most of the costs in publishing are in manufacture is just ignorant and wrong. It's been put about for years by those with an agenda to push, and been debunked just as often by those who actually work in the industry.
It's pretty obvious - few industries could cope with manufacturing costs that were 80% of the retail price, and publishing is no exception. Generally, manufacturing, distribution etc. make up less than 30% of the retail price. That's why most publishers list ebooks from 30% of print price.
But don't forget that ebooks are liable to VAT, which print isn't. That pushes the price back up again.
Unless you want for some reason to suggest that publishers ought to make less money from ebooks than print? And that sounds like an agenda rather than sound business to me.
(I work in publishing, in case you hadn't noticed, and this isn't a rant at the specific commenter. I just get annoyed by this idea that, just because there's no physical product, ebooks ought to be almost free.)