Hello GM and Developer
I will tell my idea about "How to Control Server (Duran) Economy?"
I start to find the "root-cause" by fish diagram method, and i find 1 root cause that can fix this game slowly-fastly depends on the solution.

The main root-cause is too much Cegel that player have, and the NPC is become useless when players hit lv 60.

So i suggest to make an event that have period time (u can use valentine or whatever).
1. Fast Method - Create a NPC that exchange cegels to limited permanent costume, or Pet or whatever that can attract player to spend so much cegel on it (Maybe Grabbit in the game)
2. Slow Method - Trade ur cegel for RPS Event! This event is good, and u can set the trade ratio to keep the price of soshop item in game still high, maybe u can try Grabbit with cegel (Trade for coin/ticket/whatever) and the price is RPS coupon with 1 RPS - 10.000 RPS for jackpot.

I am player that play in Duran Server, and the price is rise crazily. This solution maybe is not good enough, but for NPC i think that is only way to control cegels, in economy, inflation happen because too much money supplies.

An increase in the money supply may be called monetary inflation, to distinguish it from rising prices, which may also for clarity be called "price inflation". Economists generally agree that in the long run, inflation is caused by increases in the money supply
-Wikipedia

Thanks for the Attention,
If there are someone mad at me, is because u keep all good stuff and wait the price is growing up. Or maybe u are RMT Seller?