Laser welding is a fast and flexible way to manufacture all steel sandwich panels. Economically the most feasible solution is often to weld as large panels as possible. In corrugated core all steel sandwich panel applications the effect of an air gap in welding is difficult to eliminate when welding large panels. A system for welding large panels with a laser is often considered to be complicated and expensive. The processibility of large panels with specified core types was estimated by welding large all steel sandwich panels with two different core types. Materials used were low-carbon steel DC01 and stainless steel ASTM 304 with sheet thickness from 0.5 to 1.5 mm. The panels were welded with a 6 kW CO2 laser. The manufacturing of large steel panels was possible with acceptable weld quality (EN-ISO 13919-1). The total flatness of the panels was better than 11.3 mm, depending on the manufacturing procedure, core type, and material. Total manufacturing costs of high power CO2, Nd:yttrium–aluminum–garnet and diode lasers were compared in welding of large weight optimized panels. Laser system, panel size, fixturing, and the welding parameters affect the total costs. The size and type of the panel core has together with the batch size a strong effect on the manufacturing costs. The economical evaluation of the cost of the panel depends considerably on the application.