Is it? I might have a completely busted mental model, but I thought you only need a module-sized mass on one end of a rod the length of things we've already assembled in space (e.g. an ISS truss) and a motor to spin it.
We're space-poor. It's just too darned expensive. Even relatively simple designs are out of our reach right now, if you have to manifest them in real designs with real safety margins and real practical applications, such as being dockable.
I don't get the complaint. Assuming travel from one station to the other is impossible, what's supposed to be wrong with having two smaller stations that don't cripple the health of the inhabitants instead of one bigger one that does?
Again, the problem isn't physics or engineering, it's that we're poor in space. This, and a lot of the other posts, are basically saying "What's so hard about having a job 10 miles away? Just drive there!" to people too poor to own a car, too poor to even dream of owning a car. Yes, it is a simple problem... if space wasn't so expensive to us. (I mean, not trivial, we'd still have to redesign a lot of stuff, but there's no reason to believe there's a fundamental problem.)
The objection I questioned was "when you have to admit that astronauts won't be able to travel between those two space stations to speak of". You and wlievens are both pointing out that the scheme is unworkable regardless of the necessity of traveling between one station and the other. That's fine, but it doesn't respond to my question of "who cares that you can't travel between the stations?" It means I was correct to wonder how it could be relevant that travel between one station and the other is impossible. The objection I questioned makes no sense.
On a separate note, if Congress will fund one station, they can't object to a two-station system at the same cost. The number of stations is, again, not relevant to much.
Seems like this might be cheaper than getting it off Earth, right?
But yeah we still need to lower the launch cost per kg to make it really feasible and super heavy launch vehicles which don't exist at all at the moment. Realistically we would want to launch 40+ tons directly to mars from earth (Falcon Heavy should be ~13 tons so we would need around 3x the power of that). We don't have anything with enough delta v to do that at the moment.