Will the stars align for space-based solar power?

Powersat and a couple of other companies have some ingenious engineering that reduce the weight of a power sat to 10 tons, putting the satellite within the launch capabilities of SpaceX and the like.

I have been skeptical because the cost of a launch has always been high relative to the costs of trucks going to a ground based solar array. Powersat, however, says that its satellites will be economical when launch costs drop 50-75%, which seems achievable.

There is a second part, "running the numbers" at http://arstechnica.com/science/news/2009/07/running-the-numb...