So, as the title suggests, it is hypothetical time. Let us say that your place of residence catches fire. It is a minor fire that occurs while you are at home, and you manage to put it out before it spreads too far. The only major damage is to your Arkham base game and expansions, which are burnt to a crisp or irreparably charred. At the same time, you happen to win the lottery (or you get some unexpected inheritance, or something; this hypothetical is becoming unwieldy). Coincidentally, the amount you receive is the exact same amount of money it would cost to repurchase all of your Arkham stuff. Going down to a nearby game store, you discover that all of the Arkham products you owned are in stock. Which products, if any, would you not repurchase?
Honestly: I would buy them all. SUre, there are some that aren't that great, but I'm a completionist. All of the expansions have something to recommend them, and it wouldn't feel the same not playing an all-expansions game.
If I had to lose a big box, I'd leave Miskatonic behind before I lose any of the towns.