In Orario, all magic stones brought out from the underground city must be exchanged for money at the guild.
As the city's administrator, the guild directly monopolized the production of magic stones and used processed magic stone products to sell around the world, amassing a great deal of money for itself and the city.
Therefore, magic stones can only be exchanged for money at the guild and cannot be sold anywhere else, or it would result in being banned by the guild.
However, dropped items are different.
Dropped items are mainly used as materials for manufacturing weapons, armor, and even medicines. Although they can also be exchanged for money at the guild, one can only get the fixed market price, which is the lowest value.
The guild only monopolized magic stones, not the trade of dropped items. Thus, for many powerful families, it's more profitable to sell dropped items to commercial clans than to exchange them at the guild.