The game is definitely undervalued. That's why I donate every time i make a new character. So many hours of quality entertainment.
And I disagree with the pay for equipment idea. If I'm getting destroyed in a dungeon, it would be to tempting to buy gear, and then I wouldn't get that feeling of accomplishment when i finally overcome the challenge.
Also, the question would come into play that David may be balancing the game to encourage purchases (which we know is not true).