Trading
The player may trade with NPCs in Caves of Qud. Most commonly, players will be trading with merchants.
Trading UI
The trading screen is separated into two halves: the left half is the character the player is trading with, and the right half is the player's inventory. Here the player can offer to buy the NPC's wares off of them or attempt to offer up their own for 
water.
Controls
| Key | Purpose |
|---|---|
| Esc | exit trading inteface without an offer |
| left/right | navigate between both trading sides |
| up/down | scroll through the items on one side |
| Tab | choose to buy/sell the entire inventory |
| enter | select an entire stack of an item |
| -/= | decrease/increase the amount of items offered in a stack by 1 |
| o | offer to complete the trade |
| Space | general interaction menu. Here the player can examine objects, or ask the trader to identify or repair items (if they have the proper skill) |
| i | ask trader to identify an object (can be either in their own inventory or the player's) |
| r | ask trader to repair/recharge an object (can be either in their own inventory or the player's) |
Trading Formula
Caves of Qud has a bartering system where items vary in price based on a multitude of factors. Items do not have a "set" price like other similar games of the genre. Instead, items all have a commerce value. Commerce is the base value that is specified for each item that is then multiplied or divided by a multiplier depending on selling or buying.
This multiplier depends on the player's Ego modifier as well a few other factors, such as the Snake Oiler skill.
Trading Formula Details
If the player has Glotrot, Ego modifier and Snake oiler no longer have an effect and returns a flat -3. The equation then becomes
The multiplier cannot be higher than 0.95(achievable with +9 Ego modifier or +7 Ego modifier with Snake Oiler) and the multiplier cannot be lower than .05 (-5 Ego modifier).
When buying an item from a trader, the value of the item in question is divided by this multiplier. When an item is sold by the player, its value is multiplied by the multiplier.
Economy
Drams
The central currency to the game is clean Water, often simply referred to as their measurement "drams". 1 dram of water is universally valued at $1, and is used to pay any outstanding difference in transactions: if the player offers $32 of material for $35 of material they are required to throw in 3 drams to cover the outstanding $3 debt. Only drinking water is accepted as balancing currency: if the water is contaminated by any other liquids then it ceases to be counted as drams unless it can be purified.
It is important to note that dram exchange requires appropriate space:
- First, any containers of Drinking Water will be poured into until full.
- If the container fills then excess drams will be poured into the next Drinking Water container with space.
- If there are no more Drinking Water containers then excess drams will pour into the next empty container.
- Drams will not go into containers filled with anything but Drinking Water, as it will cease to be currency of the same value once mixed.
Having insufficient space for owed credit or insufficient drams for owed debt will result in the transaction being rejected.
Balancing Bias
While exchange prices have three decimal places of accuracy, the amount paid will round to the nearest integer. In such cases the bias always favors the trader:
| Trader Value | Player Value | Difference | Balance |
|---|---|---|---|
| -$112 | $208 | -112 + 208 = +96 | Merchant pays $96 |
| -$500 | $500.999 | -500 + 500.999 = +0.999 | Merchant pays $0 |
| -$130 | $87 | -130 + 87 = -43 | Player pays $43 |
| -$145.001 | $145 | -145.001 + 145 = -0.001 | Player pays $1 |
Alternatives
4 drams of any liquid weighs 1lb, so the weight of a filled container is the capacity divided by 4; an empty 64D water skin weighs 1lb but the same one filled will weigh 17lbs, as 64D / 4 = +16lbs. While an acceptable cost early on drams will slowly start to eat into your carrying capacity as you find more liquid containers and start selling loot, so materials with higher guaranteed $/lb will eventually become necessary. It should be noted that it is still strongly advised that the player keep one or two water containers with space so that owed currency can still be easily managed between transactions.
Liquids
Water is not the only liquid that can be traded, though unlike drams they cannot be automatically poured: liquids other than drinking water must be sold with the container as added value, so the actual profit is (Drams * 1D Value) + (Sold Container Profit - Replacement Container Cost). For example, 64D of honey always sells for $128 ($2/D), but to sell it you first need to put it in a $3 Canteen which gets you a total of $131; if canteens sell for $3 then they cost $8.574 to buy, so the final profit is $122.
Note that this table simply provides the minimum value for a container of the appropriate size, as factors like player trading stats cannot be accounted for. Liquids such as Asphalt and Putrescence are not listed as they have a trading value of $0, so the only profit they earn is for selling their container.
| Liquid | Value ($/D) |
16D (4lbs) |
32D (8lbs) |
64D (16lbs) |
|---|---|---|---|---|
| Acid | 1.5 | 24 | 48 | 96 |
| Blood | 0.25 | 4 | 8 | 16 |
| Brain brine | 1,233 | 19,728 | 39,456 | 78,912 |
| Cider | 3.8 | 60.8 | 121.6 | 243.2 |
| Cloning draught | 1,250 | 20,000 | 40,000 | 80,000 |
| Gel | 0.5 | 8 | 16 | 32 |
| Honey | 2 | 32 | 64 | 128 |
| Lava | 50 | 800 | 1,600 | 3,200 |
| Neutron flux | 1,000 | 16,000 | 32,000 | 64,000 |
| Oil | 3 | 48 | 96 | 192 |
| Primordial soup | 4 | 64 | 128 | 256 |
| Sap | 2 | 32 | 64 | 128 |
| Slime | 0.1 | 1.6 | 3.2 | 6.4 |
| Water | 1 | 16 | 32 | 64 |
| Wine | 4 | 64 | 128 | 256 |
Trade Goods
Trade goods are effectively non-liquid (figuratively and literally) financial assets. While this does free up skins and can end up lighter overall, they can only be returned to $/D value by selling them to traders. This can cause issues in some cases, as high value items require you to either trade for a lot of items or be prepared to accept a lot of drams. Additionally, dormant items carried for value do not quench Thirst nor can they provide additional uses like Lava. As such, it can be important to not convert all drams into trade goods.
| Item | Value ($/1lb) |
|---|---|
| Copper nugget | 10 |
| Bronze ingot | 20(*5)† |
| Silver nugget | 50 |
| Rough agate gemstone | 100 |
| Rough topaz gemstone | 150 |
| Gold nugget | 200 |
| Rough jasper gemstone | 200 |
| Rough amethyst gemstone | 250 |
| Rough sapphire gemstone | 300 |
| Rough emerald gemstone | 350 |
| Rough peridot gemstone | 350 |
† Ingots currently only come in bronze and weigh 5lbs