Well, Adam, you claimed that Marvel was "regularly" firing leading men and replacing them with cheaper actors. Most of the examples you've come up for this are supporting actors, not leads. And for the one case that applies, it could be argued that they first replaced the lead with a more well-known actor (Norton for Bana, hence, probably MORE expensive). So I'm not seeing the horrific trend that you claim is there.
The situation with Terrence Howard is more complicated than you suggest -- it's been reported that he was first signed for Iron Man, and that the other actors (including the star) came on for less money. They tried to adjust this on the sequel and he balked.
As for Norton, did Marvel make an offer? I remember reports that he lobbied for a more character-driven movie and didn't support the action movie that was ultimately released. I can see why they might want to recast, based on that. I can also see why he might have bad feelings and not want to return -- but for crying out loud, it was a HULK movie, what did he expect?
Anyway, jury of our peers, I urge you to convict Adam for hyperbole!