^This guy nailed it. Hi5
The guy didn't nail it at all because he oversimplified it to the level of a survey course understanding.
Traditional publishers, once they have control of pricing (which yes, Apple did give them) aren't going to see it as simple supply and demand. They also have the other arm of their business to consider. Physical books. They have huge amounts of money invested in paper book publishing and distribution. They don't want that business to go away. The overly simplistic model above does not account for that at all. They are incentivized to keep the ebook price artificially inflated in order to maintain the health of their paper book business.