The costs of the annular cylinder model are about the same as the simple cylinder completely filled with air, as the cost of the extra steel (annular model) is about the same as that of the extra air (simple model). I think, however, that the annular cylinder is preferable on environmental grounds. The annular version uses 19% of the air of the air volume of the simple model, and we should not deplete the Earth’s atmosphere more than is necessary.
The total cost of the annular cylinder model (excluding installed capital) is around $160 billion. Yes, it is a lot (note how essential but expensive water is). To put that into perspective:
The annular cylinder model costs per inhabitant are around 4 times the installed capital costs per US inhabitant for 500/sq.km. At 1000/sq.km this reduces to 2.5 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. Moreover this will fall over time as the initial cost of habitat construction is depreciated; if depreciated (straight line) over 25 years the cost of the habitat would be a charge of $17K per inhabitant.
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
Getting Started: A Starter Habitat