Who believes they are rich but are really poor in scripture? Believe it or not the entire New Testament presents a juxtaposition of rich and poor, righteous and unrighteousness, Jew and non Jew. The point is not class warfare. The point is God is turning the current worldly ways of thinking on it head. That is what the Sermon on the Mount is. That is why the first shall be last. That is why the man who submits has power.
Laodicea is simply a continuation of that theme. Persecuted churches are doing well. Thriving churches battle sin. Laodicea however, a church that has no such obvious reversal becomes the worst of all. Why? Because they think the are rich and blessed but they are really poor and despised.