Cost refers to the resources one has to pay in order to gain something in return. Typical situations are when one is recruiting creatures, constructing buildings or hiring heroes. The most common resource used in trades is gold, which is needed for almost everything. Wood and ore are typically needed to construct buildings. Mercury, sulfur, crystal and gems (otherwise known as magical resource) are also commonly used in building construction, especially for mage guilds, and usually they are needed to hire 7th level creatures.
Cost is given in the following order: gold, wood, ore, mercury, sulfur, crystal and gems. For example, a tavern's cost is given as "500 
and 5 
". If a player decided to build a tavern, these resources are reduced from the kingdom's treasury.