A player paid 600000 gold for a rare mount in WoW Classic.
We are talking about Ashes of Al'ar, a very rare but very beautiful mount that drops from the final boss (Kel'thas Sunstrider) in World of Warcraft The Burning Crusade (Classic).
Unfortunately, the chance of getting Al'ar is ridiculously low (only 1,70%), so you could spend months farming the mount, but even then there's no guarantee you'll ever get it.
However, one solution is GDKP. This is a system popular in World of Warcraft in which participants in raids or instances - after killing the boss - "place bets" on the item of their dreams. This is done in a group chat or in the raid/dungeon leader's personal account.
Thus, a player with a Chinese nickname became the owner of this mount, having paid a staggering sum of 600 gold for Ashes of Al'ar.
If you convert them into real money, you get ... 6250 USD. That's how much 600k gold is worth on the black market.
Here is what GDKP looks like (example):
Interestingly, GDKP usually works in such a way that the gold collected during a given raid / instance is then distributed among the rest of the participants.
This means that the Ashes of Al'ar cosmic deal has given other players 25k gold per head. Pretty good deal...