I got 30k and money keeps coming with even ~100 sometimes (when i got good steward + good ruler)... And there's not much i can do with it - spend it on crusades, buy new buildings in my provinces, make assasinations (though with low intrigue it is useless), give it to other rulers and... that's all, i suppose... Or maybe there's some other use of money in CK which i haven't noticed ? 