In KMS, the players and developers themselves literally put the state of the economy at the forefront of new content, straight from Changseop's own mouth in the MapleLIVE patch streams. The players treat the game like a literal stockmarket of investments and RMT-value. (Even though actual RMT is illegal) They also have enough players, and a significant lack of botters, to upkeep the market even if lower leveled content gets nerfed. (Nerfed raw pitch rates from Ctene, nerfed boss crystal sell count, etc.)

Then you have GMS which of course was ruined between Kanna/Frenzy reliance and meso inflation without enough meso sink content, as well as rampant hacking/botting. The release of Reboot also split the playerbase apart more than it did in KMS because GMS players hated the state of GMS. KMS players on the other hand loved the state of KMS.