In addition to that last post, how much income does a city provide the player that owns it? If a castle already gives somewhere around 4000-5000 denars a week, I can only imagine what a city would do.
That seems a bit much. I just checked the budget report in one of my games, and my castle was making me 2200 a week. My city was making 1800 in rent and 1400 in tarrifs.