I spent over an hour reading through community comments to understand what really happend.
Apparently, there is a bug that allows a player to bid negative values on the Auction House. After the bidding, a positive value of the bid amount is 'refunded'. :|
This bug has been exploited by the players flooding the in-game economy with millions of Astral Diamonds - the game's currency. One can only imagine the effect it has on the value. I noticed price fluctuations in hundreds, which is a little weird.
This led the dev team to rollback the server, voiding all progress made between 5:20 AM and 12:20 PM on all servers and players. Meanwhile, players who abused the bug were said to have been banned.
Yes, I'm affected by this rollback - a 6-level drop. But it's nothing really major. I didn't spend a single cent on the game nor did I buy anything in the auction house.
I'll continue playing the game...for fun.