I was just thinking about the same thing in my game.
One thing I would say about your method though, by simply adding the columns up you are giving each of those things equal weighting. I, personally, would disagree with that method.
For me the neighborhood and gameplay aspects of expansions are significantly more important than CAS and Build/Buy. I could live with weaker offerings in CAS and Build/Buy if the neighborhood and gameplay added is top notch but I'd be royally pissed if the reverse was true (because that would make it more of a Game Pack or Kit...and not worth the premium price).
I'd fill in my rankings here, but I honestly can't remember what CAS and Build/Buy stuff is even from each specific pack. I could easily do the world/gameplay aspects though.