Regarding the “charge what the market will bear” arguments … you have too simplistic a view of the market.
Digital downloads are great for the publisher. They WANT you to download from them. In fact, if they could put Best Buy out of business tomorrow and never again have to worry about their concerns, they would.
There is a certain value per digital download on the publisher’s part. It’s not equal to the extra profit they’d get there versus shipping hard product. It’s also not zero. It’s between those two. You have to also take into account market sculpting (in a new market, if you set your profits razor-thin you are shooting yourself in the foot for the next decade; you price high so you can periodically reduce prices) which pressures the price back up, hidden utility (the disc buyer can resell the product six months later; if he buys a digital download the would-be buyer in six months instead pays YOU) which pressures the price back down, and existing channel splintering which pressures the price back up.
All in all, the one thing that can be said is that when you tally the factors up for the average publisher, they end up with no substantial incentive to foster a download market. So, they sign the afore-mentioned distribution deals which instead give them a slightly better profit margin from the brick-and-mortar channel.
All that having been said, there is a significant factor - by far the largest in the above calculation - which is at play right now. How much do publishers gain from a non-fractured physical distribution market? As broadband becomes more pervasive, smaller publishers will start finding that they gain little or nothing from the retail channel which is already for the most part snubbing them. The threshold of the size of publisher who falls into that camp is increasing. I don’t know if we’ll see it plateau, or if we’ll see it climb until there is no more retail distribution. Still, right now, today, it is moving.