How much for digital?: It’s important to charge something, because the act of paying fundamentally changes the dynamics of the relationship. The question is this: at the start, is your goal to maximize profit or to build a platform that scales? The fact is that the market is too small right now for the price to matter. What matters is whether you can build an audience that is in the habit of paying you, an audience that wants to hear from you, an audience that you can build a business on.

At fifty cents a rental, all desire for piracy goes out the window, replaced by convenience, ease of use and a clear conscience. More important, entire new services show up, habits are built and the studios end up with a direct relationship with consumers who want to hear from them. If they don’t get greedy at the start. [I think Seth nailed this one.]
Source: Seth’s Blog