At 200 pop my thinking would be that the 3000 resources allows you to tech into power units faster and then field them faster.This. At 1700 HD its often simply about who gets his ressources on the map. In the end you are arguning with this exact maths for a level of 1700 HD, where the player with a bit more ressources wont win the game simply.
On the other Hand: After more than 35 Minutes of booming you will have ressources floating while being pop 200 anyway. So its not like you can get ADDITIONAL 35 mangudai. By the time you will run out of gold/ressources, your investment into trade will have payed itself.