That $10 per kilogram is an extremely optimistic estimate cited by a person who was well known to exaggerate in order to drive interest and investment.

Personally I suspect it's going to be quite a bit more than that, not that I'm an expert on launch cost. But I think we need to be a bit more skeptical of the claims being made at this time.

To the bigger question, I think any technology may be feasible in the future, but as far as I can see there's still a lot of challenges with orbital-based power. In particular the cost of sending it up and maintaining it, and the amount of power we can get generated back down on earth, and distributing that to a wide area.

But, if we don't come up with a better solution, it's definitely something I can see being in place in the next 50 or 100 years.