While some argue that SBSP construction and operations can be undertaken with little or no direct human involvement—using robotic and self-assembly technologies—I [Mike Snead] do not share the optimism that these technologies will develop to the level of maturity to enable this to be undertaken in the early phases of SBSP construction and operation.
I believe that absent a cheap launch system then we have to develop and design with robotics and self assembly and simple assembly (inflated systems) in space to keep costs reasonable. Rushing to do more with people because the robotics and simply assembly designs are not ready will continue to waste money and accomplish relatively little.
Mike Snead has a lengthy (45 page) pdf about how we could spend 100-150 billion dollars over 25 years to achieve what is basically the space shuttle as originally promised. A high frequency and safe vehicle. However, I think developing a better chemically powered vehicle is a waste of time and money.
Mike breaks out the cost for the program to develop airplane like operations.
Mike Snead has a blog on making america space faring.