Gold prodution game items can contain skills to increase your gold production and another skill called "Cautious".

Cautious skill allows you to recover max 50% of the gold invested to upgrade a city. The gold can be recovered only when you lost the city.
If you did not invest in upgrading the city, the cautious function will not give you any recoverable gold.

Cautious skill is a skill destined for Defense slots. To activate it, you need to place the gear on your defense, and not on your production slots.

Since it's a defensive mechanism, if the gear is placed on the production slots, % of the invested gold will not be retrieved.