Trade skills are passively used in towns by heroes who are dealing with traders. Those sneaky traders often manage to rip off the unsuspecting heroes so this type of skill is quite handy for such occasions.
When a hero uses a trade skill, the trader is forced to give them a certain discount on whatever they are buying, or alternatively a certain amount of gold extra when the hero is selling things. Either way, the hero manages to gain more gold than they usually would. Both of these are decided by this formula:
percentage of discount/premium = 30 + level of skill[note 1]
Recent experience has shown it seems 20% is the base amount used from published diary updates. Deities are advised to pay close attention to be certain.[note 2]
Cost-benefit analysis of upgrade
The "benefits" of upgrading a trading skill are almost invariably not worth the training costs. While the 31 percent increase in loot yield of obtaining the first level has its merits (especially since it's free), the increase to level 2 is only 0.76% higher[note 3]. Thus, at level 2, a hero would have to sell items worth 131,000 at base value in order to break even with the 1,000 gold of training cost versus staying at level 1. In other words, it is quite unlikely for your hero to have recovered the costs of training previous level before paying to upgrade again.
Conceivably, by skill level 10, a hero may have to sell a completed temple's weight in gold to justify the amount spent on tuition for each increase! (See table below)
|Level||Additional cost to obtain level||Yield increase||Additional sales to break-even vs. unskilled||Additional sales to justify last upgrade||Cumulative sales to recover last upgrade in gold bricks|
Of course, there is no way to stop your hero from "investing" in their skills other than to keep the amount of coins in hand low, such as by converting gold coins into gold bricks via encouragement before they can spend it. Moreover, having a trading skill is probably still better than not having one at all, as demonstrated by the third column.
- Assuming the admins design the game fairly, the formula for should be as discount price = normal price / ( 1 + (30 + skill level ) / 100 ). By the multiplicative property of equality, this formula would result buying skills being equally beneficial selling skills at any level. If instead the formula were discount price = normal price * (1 - (30 + skill level)/100)) then a hero with a discount level of 70 could theoretically buy all items for free (under the former formula, a level 70 buying skill would equal to a 50% discount).
- Mathematical comment: As per note #1, a discount with a base of 30% using the bold formula in note #1 would, at skill level 7, appear like discount of base 20% under the (probably incorrect) italicized formula.
- 0.0076 = 1.32/1.31 - 1