We tend to take the air around us for granted, and ignore it. I have assumed 80% of sea level air pressure on Earth ( that is, 0.8 bar) which is like living at 2000 metres altitude, which doesn’t cause people problems (at the 4000m height of Tibet or the Bolivian altiplano it is only 60% of sea level, yet that does cause altitude sickness). Yet the air to fill the habitat (that is, 565 cubic kilometres) still weighs no less than 434 million tonnes, and costs $43 billion. I have a renewed respect for our atmosphere. The numbers look much better with the reduced air needs of the annular cylinder model, cost of air down to a “mere” $10bn.
The total cost of the annular cylinder model is $136 billion. Yes, it is a lot. To put that into perspective:
The annular cylinder model costs per inhabitant are around 3 times the installed capital costs per US inhabitant for 500/sq.km. High, but not out of sight. At 1000/sq.km this reduces to 1.8 times, in the same ballpark as capital costs per person in places like New York and its commuter heartland, or South East England, where residential and infrastructure costs are much higher than the national averages.
So habitats are viable and the cost is not astronomical (forgive the pun). Moreover they are initial costs, and depreciate over time. But these calculations, as well as purely indicative, are long run, assuming an established mining, manufacturing and transport infrastructure in space. How on Earth (or rather, Space) do we get there? As the apocryphal Irishman replied when asked for directions: “If I were you, I wouldn’t start from here.”
Assumptions on cost calculations
A Starter Habitat, and its Location