http://www.highliftsystems.com/

"...which could potentially reduce the cost-to-GEO to ~ $500/kg, making Solar Power Satellites affordable. And they promise a brighter future than nukes alone."

It said $100/kg in the reference you gave.
100/kg is "apparently" low enough according to NASA studies on SPS.
I think it could possible to get to $500/kg price to GEO with chemical rockets, I'm not as confident with the $100/kg range.

I don't believe the numbers of the cost of the space elevator, nor do I think NASA's ideas of how to get electrical energy to Earth is reasonable.
"could be operational in 15 years. This first space elevator could be built for between $7-$10 billion"
I think NASA could study it for 15 years and have it cost 7-10 billion- maybe, it could easily cost more- but forget about actually getting to point of building actual hardware.