<p>Cost calculation is necessary for welded structures because manufacturing processes such as welding and cutting are energy-intensive. The previously developed cost calculations have been modified to incorporate welding speed and time information from other welding technologies. Some Japanese companies that make welded structures provided us with data on different welding technologies. The cost includes material, welding preparation and actual welding, plate flattening, surface cleaning, painting, and cutting. All these costs directly affect structural dimensions, including plate thicknesses and other dimensions. The optimisation model includes the objective function, the cost, the unknowns, the structure sizes, and the design constraints to determine the best solution. Other cost elements, such as transportation, amortisation, investments, design, and inspection, are not considered here. Using the new dataset, we have optimised a stiffened plate, and we can compare specific fabrication costs as production moves from an expensive, developed country to a cheaper one. In the stiffened plate optimisation example, the number of stiffeners increases, and the thicknesses decrease in all cases. This means that the structural sizes depend on where they are made.</p>