http://www.thespacereview.com/article/1579/1

And that was just several short missions to a world 3 days away, not a semi-permanent 100 man base to a place nine months away, one-way. What would it cost to maintain something like what we now have in Antarctica on Mars? Just the LEO infrastructure needed to support that base logistically would be prohibitively expensive.

I think we need to get realistic. Manned exploration, much less settlement, of the solar system is just not in the cards unless one of two things happens, preferably both.

1) Drastically more efficient (at least an order of magnitude) propulsion and life support systems become available.

2) Something is found of such enormous potential value (an alternative biochemistry, or artifacts of an extraterrestial civilization) to make it worth our while.

I'm all in favor of increasing our spending in space tenfold, or more, and I'm convinced that it will pay for itself handsomely--in the long run. But manned exploration for its own sake will be just as disappointing in the future, on a per dollar basis, as it has been in the past. We're better off putting our money into robotic probes until we find something worth going after no-holds-barred, damn the expense. I am confident it is only a matter of time before we do so, and our chances improve the more places we visit, not the more time we spend in any one place.