[giantrobot]

Their math is wrong. The ISS solar panels plus supporting truss elements mass about 60t or 2KW/t. At the fantastical (unbelievable) $20/kg to LEO that's $10/W. That doesn't include the mass of thermal control elements, maneuvering systems, power conversion, or power transmission system.

Also that's only to LEO which is useless for an SPS since the system wouldn't dwell over any receiver on the ground long enough to transmit a useful amount of power. You'd need all that mass in a geosynchronous orbit which trebles or quadruples that cost.