There was mention of self-sufficient space settlements on one of the mailing lists I subscribe to. I thought about that, and concluded that we will trade far more between technologically advanced space settlements than we do between people on Earth.
From my own electronics/semiconductor experience:
Electronics depends on semiconductors. A wafer fab might turn out 250K 200 gram wafers a year - about 6 hectares and 50 tonnes of nanometer-accurate surface-patterned silicon. The fab, offices, workers, homes, and local support for the fab might be 10 million tonnes of buildings and roads and schools and grocery stores.
I emailed a friend who helps install and maintain the stepper (photolithography patterning) tools for the local Intel fabs. Two cargo planeloads are needed to ship one of these tools (perhaps 50 needed) from the tool manufacturer, not counting the power lasers and other systems. All the sophisticated fab tools might be produced by 50 suppliers and 100,000 technicians around the world, and weigh 3000 tonnes (WAG). They are surrounded by far more structure and wiring and plumbing and filters, and use hundreds of megawatts of electricity and millions of gallons of water.
So, do we ship fab tooling (which goes obsolete in 2 years), or silicon? Until the population of the space settlement is as big as a large city, we ship finished components and assembled electronics systems. Until the settlement is as big as California, we ship silicon wafers. Until it is about one billion people, we ship production equipment. Until we have nuclear transmutation, we ship raw materials from places where the geology beneficiates them.
We live in a global economy where ASML (Dutch) steppers are shipped to Japan and Nikon steppers are shipped to Europe. It is hard to imagine that we won't trade even higher volumes of specialized goods across planetary distances. The costs will be high, but much less than the cost of duplicating a global economy, or doing without the benefits of one.
Hawaii even imports gravel for concrete. We will ship stuff as dumb as gravel over interplanetary distances for a long time.
Welcome to economic interdependence.