re: How much will it cost?
This article gives more detail:
Inflatable tower could climb to the edge of space.
* 08 June 2009 by Jeff Hecht, Boston
http://www.newscientist.com/article/mg20227117.000-inflatable-tower-could-climb-to-the-edge-of-space.html
It gives the fully pressurized tower made of Kevlar a total weight of 800,000 tons. Kevlar is however more expensive than steel.
Bob Clark