The dupe you're talking about must be infinitely repeatable if it's already in the hundreds of millions. I really want to know what it is when it blows over, out of curiosity's sake and out of EQ knowledge lore.
Ya'll wanna hear one of the ballsiest dupes I ever did? There was this bug where if you died in a particular way, your corpse would poof entirely. This was around 2008ish I believe. So the first time this happened to me, I petitioned, and got my stuff restored. Well it just so happened that when this happened, I had put several million plat from my character that died to the shared bank 10 mins before I had died. I noticed I had my plat back, and it was still in the shared bank.
So I rinse repeated this over and over again. Spacing them out and swapping accounts etc to avoid being known. I did it about 10 times before I figured any more and I'd be caught. The way the death happened was very subtle, so it wasn't as obvious as you might think, and I made it appear like it was a unique, specific zone line that was doing it. And the gm's were too lazy or stupid to check that I was putting plat in my shared bank each time. Duped at least 100+ million, all by GM's restoring my characters plat for me after I'd put a bunch in the shared bank. lol. Never got caught in any way. But there were eventually patch notes about dupes in this manner. So I imagine someone else was doing it too or maybe they knew about me but didn't punish me? I'm assuming the former and not the latter.