Most of that gold is from bots. Normal players simply do not have large amounts of organic gold to trade off. You are swapping with bots, or people who traded with bots, or people who took botted gold from GDKP pots.
I am tired of this totally dishonest argument that bots, gold swaps and GDKPs are not a racket and front for gold sellers and that it has not destroyed the game in every version. The economies of Era and Wrath are completely ridiculous and its not from honest play. I am glad they are doing everything they can to lessen or at least slow the destruction of SoD, including banning people in possession of gold that was botted at some time or another, and that the laundering and dissemination operation that was GDKP is gone. It’s a few steps in the right direction.