Mudflation
Inflation in a virtual world: when items and money keep pouring in and nothing ever leaves, everything loses value.
In a MUD, every slain monster conjures fresh gold and loot out of nothing, yet very little ever leaves the economy. Swords don't wear out, gold doesn't rot, and veterans hoard more than they could ever use. A few years in, newcomers can get hold of gear that was once legendary, so the admins add even stronger items to keep the old guard interested — and round it goes. The word comes from 1990s MUD administrators, particularly in the combat-heavy DikuMUD family.
The cures are known as sinks: repair bills, taxes, items that break, fees for travel. Players hate every one of them. The problem followed the genre faithfully into the MMO era, and economists have since studied game worlds as laboratories for monetary policy with unusually compliant test subjects.