Spacecraft solar array engineers now have cell choices running from inexpensive and less efficient silicon (Si) cells, to gallium arsenide on germanium (GaAs/Ge) cells, to more expensive and efficient multi-junction (MJ) cells. This paper finds that the more array weight can be reduced by using more efficient cells, even when they are a very expensive option in terms of the array alone, and put into the spacecraft payload i.e. the scientific instruments or in the case of commercial spacecraft, the communications equipment, the more cost effective the spacecraft array system. This is true for a wide variety of spacecraft. This is because of the very high price of launching a spacecraft payload and supporting it with a spacecraft.