There's a much longer report here:

http://www.islandone.org/MMSG/aasm/

It's one part of the results of a NASA workshop on the concept. Another related part not included in this web reference is section 4, which involved melting down and re-using space hardware -- especially shuttle external tanks -- in an orbital manufacturing complex.

These are high-level engineering studies, basically back of the envelope calculations that prove the concept feasible. The growth rate calculations are probably fairly accurate, but cost & development times require a project plan which this is not. if you have a few million dollars you could get it costed out though.