It strikes me that the economics of product "bundles" seems to be one of those things that's just inherently hard for people to understand: http://www.isegoria.net/2010/04/paying-for-channels-you-neve...
Every business has a fixed cost component. Content production would be no different
What major sunk cost is the publisher carrying, directly or otherwise? Digital distribution? That's not a zero dollar cost, but it doesn't cost hundreds of millions of dollars either, even if they can find someone who'll quote such a price.