I don't agree that Moulds is a quitter but I also don't think he left for the money. He received a $5 million signing bonus and $9 million over 4 years. Usually the base salary in the first year is low because of the signing bonus. So let's guess that his salary is $1 million the first year, $2 million in year 2 and $3 million in years 3 and 4. EM was scheduled to make $7+ million this year from the Bills and his agent said he would not take ANY paycut. And I would guess his salary for the next few years was much higher than $2-3 million per year.
We don't know how much of a paycut the Bills were asking but the Texans contract seems very reasonable dollars-wise. I think the Bills would have been happy to give that to him.
I agree with the rest of your post and there is no denying that EM had many other reasons to want to leave (although I'm still disappointed that he did) but I'm pretty sure money was not one of them (sadly, it would actually make me feel better if he did only leave for the money).