I did say it was simplistic and i just used them number because they were easy to divide. However it still stands that a courthouse only gets rid of 50% of corruption in comparison to 25% gained with a grocer or market. which ok if maintenance is minus 20 gold is a lot but we dont have any cities like that. And as we are a financial civ then cottages are the way forward and so, the majority of cities will be raking in quite a bit of gold. If not whats the point in a financial civ?