A few points to make before going into the economics of orbitals.
1) FF&S-2 has values for "Extended Life Support" from "Vat Grown Algae" to "Yup I like Beef". Before making up your own numbers from whole cloth, take a look at them. they range from 100 to 1,500 m³ per person, with pop minimums of 25 to 75 (more extensive habitats have higher mins)
2) Biosphere 1 was a debacle: please don't use it as a base for anything serious (they flushed the air supply "on the sly" repeatedly, and a crew was insufficient to maintain the internal systems...) Lessons were learned, but it was *not* self contained.
3) if you're "poor" you're probably living in something like a college dorm anyway, If you're rich then you can afford a nicer spread. In Vancouver $2,000,000 either buys you 1,500 square feet near the top of a tower downtown, a slightly run-down home in the "good" part of town across from the ocean / beach, a nice house in one of the "good" parts of town with an ocean view, 4 "average" 3 bedroom houses, a fairly large acherage inland 30-40 minutes from the city, or your own private island in the northern gulf islands. the "choice" between "quality" of habitat or "Quantity" of habitat is already here, most folks just aren't used to thinking that way.
4) You're using the wrong paridigm for habitat construction: you will find that the cost for 2,000 square feet of living space is much greater in a yacht (or cruise liner) than in a house. Yes, the "house" must be pressure tight, but floating houses (we have them here) are generally close to the "square foot" construction costs of "standard" houses (they use more prefab components, but then no-one expects them to be built the same way as "normal" houses)
5) A lot of the cost for current construction is based on the cost to drag it out of the ground, transport it to a refinery (whether this is a sawmill or a smelter) power to refine it and the cost to ship it to the construction site. If you are doing this in orbit (and have fusion rockets) most of your "transportation costs" approach 0, your cost for refinery energy is amortized over *decades* if you are using solar arrays, and your cost to "dig it out of the ground" is minimized if you have planetoud belts. As a result, orbital construction costs (once you have built the infrastructure) will be significantly lower than "planetary" construction costs, even ignoring efficiencies that having ready access to vaccum (without having to pump the air out) gives you.
I think that perhaps too much is being made of the "cost" of these archologies. What is the "cost" of a current home? My house, on a 33x120 lot in sunny (not) British Columbia is currently valued (tax assessment) at over $400K . The "house" value has doubled in the last three years, to a massive $30K, so that 33 x 120 (~ 400 square meter) chunk of dirt is "worth" about Cr100,000. What's the cost of 100 square meters of hull and dirt? One of the reasons that real estate is such a "good investment" is (to steal a line) "because there isn't any more of it being made"
There is *lots* of money to be made in selling the suburban (suborban?) dream, and with a planetary population in the 10's of billions and (relatively) inexpensive orbital / interplanetary transit you're looking at an economic situation where it's probably *cheaper* to buy into an orbital archology than to buy an appartment on planet.
And you can't tell me that those developers who are currently making a killing selling subdivisions of exactly the same cookie-cutter houses can't do the same in space? (they'll probably have the same problems too

)
Pro's: Pick your climate, don't be bothered by rain etc
Con's: The relatives get a bit freaked out by having the "ground" hang over them like that (spun habitat)
Pro's: Mother in law won't visit, due to aformentioned Con.
...
If you have a system pop in the 10s of billions and the capability to build archologies (A or B starport) then you have a MINIMUM of tech/9. If you can build starships, you have a min of Tech/11, and if your homeworld sucks in any way, that also increases the base tech (and reduces the effective "cost" of the habitat). This also INCREASES the number of people who would see orbital habitats as an attractive alternative.
If the atmosphere is "tainted" in any way, then you're living in archologies *anyway* and a cylindrical archology will give a lot more space (cubeage) than any ground based habitation, since you're only paying for the surface area (the hull) not the volume enclosed (ok, air will cost a bit, but that's really stretching it...)
Even Robject's "Trade Minimums" are trivial: Archology 1 produces machine parts, and rades with Archology 2 (electronics) Archology 3 (fine art / entertainment) Archology 4, 5 and 6 (Ag, forest products and sushi respectively) while getting materials from Rockball 2 (silicates and corbonates) Daedalus Fuels (gasses) and Belter Consortium 318 (metals and rare earths). For large production runs on energy intensive products, excess power is provided by trading with Solar Farm 226 for beamed power, although their "anchor" client is the bulk smelters owned by Belter Consortium 318.
Most of the infrastructure would be supported by *taxes* just like any other large public works. We just don't have any experience with "the world" being a public work.
No "superfund" sites, since anything really polluting is just packed up and parked in a holding orbit until someone decides there is something in the "junk yard" that can be more economically processed from waste than refined from raw materials.
Chances are you'll be using passive solar for generation, both because it will probably be much lower maintenance than running a reactor, but also because your "air" is probably largely generated by converting silicates into silicon and O&sub2, which leaves you large piles of purified (or partially purified) silicon which has few "construction" applications other than solar cells and other "low quality" electronics ("High tech" electronics will probably use carbon semi-cons: diamond can handle more heat than silicon...)
Anyway, you get the idea, and yes, I will eventually get around to populating the "other deep space facilities" thread...
Scott Martin