If you use an item with limited uses in a shop before paying for it and in the presence of a shopkeeper, you will be charged a usage fee. This includes items with charges, spellbooks and non-permanent light sources.
Messages associated with usage fees
|"This is no free library, cad!"||spellbook|
|"That will cost you (n) zorkmids (Yendorian Fuel Tax)."||potion of oil|
|"Usage fee, (n) zorkmids."||all other items|
Each of these messages has a one-in-three chance of being prefaced with "Hey!" or "Ahem."
Usage fees are a percentage (rounded down) of the item's normal cost:
|Item class||Usage Fee||Notes|
|Magic lamp||See below||See below|
|Magic marker||50%||No matter how many charges are used, or even if the use was successful|
|Bag of tricks
Horn of plenty
|Can of grease
|All other chargeable tools
|25%||Only if the item had any charges|
|Potion of oil||20%|
The usage fee of a magic lamp depends on how it is used:
- 'a'pplying it will be charged as if it had the price of an oil lamp
- #rubbing it will, if a djinni is released, have a usage fee of 133%
In general, it is preferable to buy the item first (credit cloning), or even buy/use/sell it. One exception might be low-level spellbooks: By the time the spell expires, your character will likely have found another spellbook of the same type, enough gold to buy the first, or an untimely demise. However, it is rarely difficult to find the 20 or 40 gold which makes the difference between buying and paying for the use of the spellbook. Another possible exception might be for an early wand of wishing: a paranoid character might choose to use the wand to first wish for scrolls of charging, and then wish for sufficient gold (up to 5000 is guaranteed) to pay for the wand and usage fees. This wastes a wish, but for characters/players with high mortality rates may be worthwhile. Again, it is rare that this will be necessary; between selling items and finding gold on the ground, most characters should be able to scrounge up 500-1000 zorkmids for a wand of wishing. Alternatively, one may wish for something to kill the shopkeeper with.
- shk.c in NetHack 3.4.3, line 3922: usage fee