Cost (Improvement Properties)
Determines the base cost, in shields, of building the selected improvement/wonder. Note that this value is multiplied by a cost factor which determines how many shields it actually costs to build the selected improvement/wonder. The human player’s cost factor is always 10. Depending on the difficulty level, the AI’s cost factor can range from 20 (Chieftain level) to 6 (Deity level).
The AI cost factors can be modified via the difficulty levels page.