yeah I dont get people saying it is ojnly the payoff of one good city.

You can NEVER make a conquest giving you 5000 of the bat; my merchant trade tends to be around 15k a turn regardless of the faction i play (unless im playing pure mayhem like moors right now)
Granted there are some regions that will net 5k a turn after a bit of development after you conquer them but they are a minority : Genoa and Venice; Antioch if you can get it stable; stockholm.....

no i'll keep my merchants thank you very much.