Fixing MapleStory

There should be some level:price ratio (A single cube being 50-60k mesos between 1-20, while between 180-200 it's 15m).

Doesn't really make sense, people would just cube on mule accounts. Different cubes for each tier of potential though does make sense since you only get 2-3% from level 30 equips where you'd get 6-9% on higher stuff.

Fixing the exchange rate just needs some meso sinks that rich players will use. If you put anything actually consumable on sale for mesos (cubes, WS, MEEs, etc.) then the rate would drop soon enough.

You do have to deal with the botting/hacking problem before any ingame achievement has value though. NX can preserve its value only because botters can't generate it.