Hidden Cost Edit
Training these units at a factory requires 98 seconds (93 with Team Engineering School sent by a Chinese ally). The average gather rate of a Factory is 5.5 every second (before the building upgrade (+20%) and Home City Card, Market, etc upgrades). This means that Heavy Artillery produced from a Factory, while appearing to be free, will have a cost dependent upon how effective the factory gathers a needed resource. In many cases this cost can exceed the base value (600 resources) of the unit.