Keyword: Inflation
TL;DR ? --> just read the bold text.
we have seen such an extreme rise already around 2(?) years ago. Back then it came from an uncontrolled flood of adena hitting the Servers. That Adena was just created without any counter value to it and came from Elcyum Powder that was sold to NPC Grocers. The source of that Elcyum powder was the huge amount of players that started fishing with the newly introduced Fancy Rods, that were much faster then the normal rods. A player that collected 4 Powerfull Fish could exchange those with the Fishing NPC and received 3 Elcyum Powders in return, which was then sold to the Grocer NPC at a price of 2kk. The success rates were pretty good so a player could make a pure profit of 800kk to 1b per week. But, as i said before, there was no real value against that and the NPC just "create" Adena when they buy items from players so there was a huge Inflation of Adena which drove up the market prices at similar rates like now. This was all stopped with the change of the Fish-to-Elcyum exchange rate from 4:3 to 12:3 and later with by lowering the NPC bid price down to 1kk per Elcyum Powder.
Now, there is a new form of "Adena printing" that has no real work value against it. Everyday, some top players pull a minimum 10 b Adena from the Cursed Sword System. Compared to the Fishing-System, there is a difference in the distribution of the Adena, cause with the cursed swords, only some top players get their hands on the "new" Adena. Nevertheless, we all know that this small circle of entitled players sells a huge amount of Adena to external (illegal) Adena Sellers for real money, thus the Adena makes it way to the large player base, flooding the market and driving up prices.