The Mishna says: If a man says to a woman, "Marry me. I am rich.", and she agrees, but it turns out he is poor, the betrothal is not valid. If a man says to a woman, "Marry me, even though I am poor.", and she agrees, but it turns out he is rich, the betrothal is also not valid. [Kiddushin 48b, see also Shulchan Arukh, Even HaEzer 38:24]
The Gemara asks: Why the second? Because she may say, "I do not want a shoe that is too big for my foot." [I.e., I do not want to marry above my social standing -- my husband may act haughtily towards me and I also do not want to constantly worry about whether I am using the right fork for the fish.] [Kiddushin 49a]
My question is: The Mishna and commentaries assume that "rich" and "poor" are clearly defined. Are they? I could not find precise criteria anywhere.