Orbital Economy

I've been thinking about the problem of finding extraterrestrial
gold, and I was wondering if someone wiser than I would pick this
idea apart:

Orbital Satellite Manufacture. We currently have to launch all
satellites from the Earth's surface. Satellites are used in several
industries, including communications, entertainment, military and
science.

If the satellites could be manufactured in orbit, the cost of lift-
off would be eliminated.

The problem that comes to mind immediately is, of course, resources.
With solar power collectors and automated assemblies, the main issues
it seems to me are materials and maintenance labor.

What other problems/advantages does the group see?