I'd argue that there doesn't have to be any secret reason. You say that greed "is a given" as an argument that there must be something mysterious going on, but raising prices when you can get away with it is no less a given.
The mystery is why you can get away with it. Bezos famously said "your margin is my opportunity". Why is there no Jeffrey Bezos waiting to pounce on the opportunity?
https://news.ycombinator.com/item?id=36483676