There realy should be option to have dynamic building cost. Instead of having fixed building time and cost like 3 tears and pay 250 gold there should be opion you can spend more money to build faster or less money to building take longer to build.
Building cost should consist 2 elements. Building material what is fixed and have 20-30% total building cost and workers salarys what is 70-80% of building cost. But ruler can spend more money on workers to increase building speed.
Building cost should consist 2 elements. Building material what is fixed and have 20-30% total building cost and workers salarys what is 70-80% of building cost. But ruler can spend more money on workers to increase building speed.