CharlesRyan
Adventurer
Electronic content can be published very, very cheaply compared to wood pulp.
While I don't want to shoot down the idea of support through DDI (which I think is a good one), this is a misconception that fuels, among other things, a lot of the debate on PDF pricing.
Production costs are a relatively small factor when it comes to publishing on WotC's scale. Development costs far outweigh the cost of the paper and printing; the savings in going electronic are not insignificant, but are pretty minor in the grand scheme of things. (Compared to smaller companies, WotC's large print runs drive production costs down; their high production values drive R&D, art, and design costs up. Even in small companies, anyone paying their designers a living wage spends more on development than printing.)
Electronic publishing does reduce the time to market and eliminates a lot of logistical headaches, which makes it well suited for riskier endeavors such as supporting campaign settings. (And that alone is a bit of a cost saver.)
But ultimately, while there are a lot of real advantages to electronic publishing, saving on print costs is pretty minor.