Isn't Item Rarity affecting gold drops actually really dangerous for the currency exchange?

So the gold tax on using the currency exchange is basically the only thing stopping bad actors from manipulating the prices right? Isn't having more variable multipliers for farming gold really dangerous for that? Gold drops have to be high enough by default so anyone can have basic access to trading, but if groups stack multipliers to gold drops and generate insane amounts of it super efficiently then they can essentially bypass the one thing stopping them from mass scamming the entire currency market.

Item Rarity might not single-handedly enable such a thing, but it does make it easier. Having too many ways to boost gold drops is really dangerous for the entire trade economy.