
This feature can be used for the following purpose:
1. Gold is hardly useful for non-dwarf players in middle-game and even late-game. After gambling in the 2000g randarts, money is mostly a useless number. For infinite dungeons, money even become completely useless. This system can make the purpose of the monetary system better.
2. As the number of artifacts gradually grows, it becomes even harder to find a suitable artifact or complete a set. Though luck is also a important factor in roguelikes, I think more chance to choice makes things more variable.
3. There are not only items for buying. Escort trees and talents, elixir ingredients (to get access to alchemist quests faster), even treasure maps. Yet again, that is more valuable for infinite, making some campaign-only builds become accessible.
Markets in dungeons act as a special vault. Instead of defeating enemies to get reward, its a 'Equal Exchange'.
In it there are some mysterious merchants and brilliant treasure located on the floor. Things there are mostly better than ordinary vault loot, but its cost is also astonishing.
In early game, only some ordinary merchants will spawn, like halfling hawkers, angolwen apprentice and dwarven ambassador, as game goes through, you can see even more merchants from everywhere, as yaech hunter, rhaloren corruptor, anothils, nagas, golems, dragons and even demonic beings waiting you to sell your soul for an appropriate price. Goods will varies from merchants.
For pleasure, an additional challenge mode can be added : just pick up things without attending to paying the money! That will let merchants become angry and spawn its powerful fellows. In this status, you are hunted like in insame mode and will face some nearly immovable bosses. They may even lock the floor of this floor for some turns and use a Sher'Tul device to block your Rod of recall. Your only choice here is try to run and fade until the clock knocks. However, if you take down that guardians, though nearly impossible, you will get a unique artifact can't be found anywhere else!
Some additional settings can be added, like, you may miss the goods forever if you decide not to buy it.