Speaking specifically about books, authors typically only make something like $0.25 per book sold. So if they started selling books for $1 and made $0.75 per book sold, that's a 300% increase in revenue from their books, and potentially a lot more books being sold since the price is 1/15th the cost of the dead-tree edition (assuming $15 paperback price).
I think the one thing missed here, and throughout this thread, is how this valuation comes about. Writers don't publish their books (in general), they rarely market them, and they even more rarely work out sales for them. In short, writers don't bear the burden of risk like the publishers do, so they don't get the spoils of success like publishers do. Moreover, most writers are offered that 25 cents per book sold as a lump sum advance plus royalties. In other words, the publisher is reasonably certain a minimum number are going to sell and they provide that as a lump sum up front. Then the writer gets ongoing royalties based on the number of copies sold. Where is the risk in that? Now I realize this only applies to established writers, but it is those same established writers who's books you are (presumably) looking for, otherwise you would see them on the indie sites and not question this. Moreover these same indie writers are looking for that big lump sum up front (+ royalties) to indicate they made it big. It means they can concentrate more on the writing and less on the marketing and it also means they have less worries. Why would they move to something like you are mentioning even if it does pay more - it is more work as well.
From the publisher's perspective, things get even more harried. After all, customers are asking for digital version. This is a good thing because it is cheaper to produce and distribute. On the down side, marketing is much more fractured so it is more expensive, though this is offset by the fact that all avenues are cheaper due to the impact of the internet - so call that a wash. Then there is the whole control issue. Digital media is SO MUCH easier to copy and it becomes cost effective (printing is not nearly so cost effective because the materials cost nearly as much as buying a book). Then there is the fact that because it is digital, there really is no such thing as economies of scale. After all, to get more people to buy requires bigger, better, faster servers - there is not really anything that make it cheaper at the 100,000 copies vs. the 99,000 copies. Often this is where manufacturers make their money - it is actually cheaper to buy it legally then to make a copy. So now to offset this, you have to consider DRM so a) you don't loose money and b) so content providers will consider using you to publish. So now you need to be a DRM expert and know what is broken and what isn't, how it is broken, how it is maintained, etc. This comes with it's own costs that - again, really don't have any significant economies of scale. Moreover, when it is broken (and if it is electronic it WILL be broken), you need to know what your next move is and have the money available to make that move when it becomes necessary.
So in short, the answer why digital media costs so much is the costs went down, but the risks went up so the cost stayed the same.
A better question is how can you create a business proposition that does transfer the extra risk to you, but does lower the WORK and WORRY on the writer while lowering costs for all involved? That is what would be needed to be adopted, as once the content is there, the people will come. As the saying goes, "Content is King". Now, extrapolate that from books to all content - music, programs, whatever.