you'll need a few triggers:
Trigger 1: City Counter
The event/condition depends on how you capture a city: let's say that you build a city, and everytime someone destroys it, the city respawns but for the player who destroyed it (very lame, but this is just an example)
Event: unit finishes constructing a building
Condition: unit comparison - constructed building = City
Action: set CityCounter [Player Number of owner of constructed building] (Integer variable with an Array of 12) = CityCounter [Player Number of owner of constructed building] + 1
Trigger 2: Whenever a city is destroyed, it should respawn and change ownership to the destroying unit
Event: a unit dies
condition: unit type of dying unit = City
Action:
set CityCounter [Player Number of owner of dying unit] (Integer variable with an Array of 12) = CityCounter [Player Number of owner of dying unit] - 1
revive unit instantly
change ownership of last revived unit to owner of killing unit
set CityCounter [Player Number of owner of killing unit] (Integer variable with an Array of 12) = CityCounter [Player Number of owner of killing unit] + 1
Trigger 3: The actual income
Event: Every X seconds of game time
action:
loop - for each integer A from 1 to 12:
do:
Player - Add 200*Citycounter [Integer A] to player [Integer A]'s gold
didn't use world edit to create these triggers, so the exact trigger might look slightly different, but basically, this is what you should do.
if you capture a city in a different way, ofcourse the events of trigger 1 and 2 should change, or nothing will work.
EDIT: you replied before I posted... didn't know.
tell me how capturing a city works, and I'll see what could be done