While I believe they saw these numbers, specifically that lowering the price from $15 to $10 lead to a 74% increase in purchases, I don't believe that this is a good general rule of thumb. Here's the problem: there are only so many potential ebook readers out in the world, and they only have so much time. This means there will be market saturation at some point, or at least market movement. This elasticity is there,…
The reason is: paper. Dead tree books weigh a lot and waste space. Therefore owning a library is a cost. Costs to move, costs storage space, costs effort to collate and maintain and protect.
E-books do not have that cost. Having a hundred e-books in your purse is a normal thing. Having a thousand? Well, it might make sorting through your personal equivalent of a branch library a little more fussy, but it won't weigh more or waste space.
People may not have more time, but they can divert time to books, and they can divert re-reading time to new-book reading time.