Until we've done a detailed cost analysis, we really won't know for
sure whether it's less expensive to use the space station or to build an
assembly fixture in a low-inclination orbit. We do lose about 10,000 lbs
of payload to go to that higher-inclination orbit, but we have to weigh
that against the cost of the assembly fixture. Using the Titan IV
launcher, it looks like we'd have enough payload margin to rendezvous with
the station anyway.
The big cost driver is launch. With launch costs coming down, we
might anticipate that the development cost for a new LEO facility could
become significant, even one as simple as the facility we've envisioned.
Another big driver is the cost of getting anything certified to approach the International Space Station. Several commercial space flight companies have looked into using the ISS as a base for their operations, only to find that they would have to spend more money certifying their spacecraft to operate in the vicinity of the ISS than they spent on developing and operating their craft. This tends to drive commercial space flight to use other facilities, to the detriment of the International Space Station program.