Having done some testing: on a standard map, on noble difficulty, each city that is 7 tiles from your capital costs 1 dollar per turn in distance costs.
For example:
If you have 6 cities, each 7 tiles from your capital then your distance penalty is 6. If you have 4 cities 7 tiles from the capital and 1 city 14 tiles from the capital, then your distance penalty each turn is 6.
If you have 3 cities that are 4 tiles from the capital, and 3 cities that are 10 tiles from the capital, then your distance penalty is 6.
Does anyone know the formula for maintenance costs for cities. I haven't figured out a way to test that yet...
For example:
If you have 6 cities, each 7 tiles from your capital then your distance penalty is 6. If you have 4 cities 7 tiles from the capital and 1 city 14 tiles from the capital, then your distance penalty each turn is 6.
If you have 3 cities that are 4 tiles from the capital, and 3 cities that are 10 tiles from the capital, then your distance penalty is 6.
Does anyone know the formula for maintenance costs for cities. I haven't figured out a way to test that yet...