Digital content has to be cheap because it's worth much, much less than physical content due to lack of resales.
True, but given that I wait for said massive sales actually means that I end up paying LESS for my games(on average), than the difference between buying a game new and then selling it to a store like gamestop, and as a bonus I get to keep my game!
So I'd argue that it's not worth that much less, and I still remember reading an article where the author argued that the resale market for games, especially server-dependent online ones, actually drives the price for games UP, and that the continuing profit TO the studio from steam-style sales provides incentive to keep improving the game. His arguments were quite well reasoned, even if I didn't agree with all of them.
Of course, this is getting away from e-book sale prices a bit. You don't normally expect to see revisions to a published book, even though such would be possible with a e-book, and such may not be welcome. "Han shot first!" type stuff.