I think the main money issue is that the PHB, DMG, and MM all sold for about $20. And they were good quality hardback in color. They easily lasted a long time.
Next come all the suppliments. These are $30, paperback, and black and white. Not only that, but they seem to always need some major errata, as much as the entire PHB, and it's only a quarter of the size. They don't follow the same format (are the spells in the front, back or middle?) and almost require the web suppliment (TaB anyone?).
When you compare the books, you can see why people are upset about the cost of the new ones and, really, who can blame them? It just seems as if they could just make their money after dropping all the other features, but the price is also uped.
Don't get me wrong, I can understand the other side of this too but it is an issue with all us poor gamers.
It's also another reason why all the new (and sometimes uneeded) projects that go on at WotC scare us on occation.