It happens very seldom, twice a month at most, when the old RNG gods decide to favor us with what I nicknamed the perfect storm.

The following circumstances need to be true for a perfect storm.
2000 gold Emissary for War Effort
2000 gold Emissary for a zone
An invasion assault in the same zone

What does that mean? You get 20,000+ gold for doing 4 world quests. If your teams are established, 2 in 5 will also receive 4500-5000 gold paragon reward.

Last time I used 7 teams of 5 and made a bit over 210,000 gold and took me 41 minutes. I have recently finished leveling my 9th team, but now with flying I bet it takes half hour tops because most time spent is travelling.

The next possible perfect storm for Horde will be in 8 hours, the next assault must be in Vol'dun. You can check the time here.

Good luck and get rich!