"I'm assuming that we are not talking about a tiny little one-room outpost which is capable of sustaining human presence for only a few hours at a time (like the Apollo landings where the only shelter for the astronauts on the surface was the LM, with limited life-sustaining resources), but a true outpost which has both the life-sustaining resources and research capacity to be manned long-term."
When I said less than 1 billion, I meant sustaining human presence for days to weeks- not months. Otherwise, I recall giving a cost for a particular base.

"The thing with a lunar base is that one has to do the preparatory work first. With the few Apollo and Lunar Surveyor and Prospector missions, we still don't know much about the geology of the moon, which would probably make the construction of a subsurface lunar base dicey. If one goes ahead with it, there would be a need for detailed survey missions ($$$)."
True, but it gets back to why are you going to the Moon, perhaps studying the Moon "geology" is a main factor in why you are going there.

"Then there is the question of hauling the construction equipment and material to the moon if one wants to actually build on or below the surface ($$$)."
??
You would need them?

"Or if one wants to go pre-fab, it would be either multiple launches of small prefabs direct to the moon or build big prefabs in orbit first (same concept as the ISS and probably cost as much)."

I would think that in terms of a large base or small base, a large base would definitely require significant sheilding, since a large base at least implies a more permenent occuptation of the base. So this means you want some regolith between living quarter and the sky. This means you either bury the base or use something like a lava tube.

"And of course the $$$ needed to sustain the presence... Somehow I don't think a moon outpost that is manned only a few days out of a year can justify its cost.
That's why I'm kind of skeptical that the Chinese mean to accomplish that by 2015. :-P "

To me, sending crew to the Moon makes "economic sense" for NASA to do. By which I don't mean that NASA is going to "make money", but rather it would be a step to possibly encouraging the private sector to commerically mine water on the Moon.
Now, if the Chinese plan is NOT to send crew to the polar region, then I would suspect their program is geared more around "PR" & it would be a rather limited program.
If the Chinese are planning on Lunar polar mission, then it's just as possible for the Chinese to be commerically sucessful, as any American company. And if the Chinese wanted "PR" and commerical success, then there is no reason why they couldn't involve international companies "in this venture".
I don't have the bias that the Chinese are stupid and incapable.
The USA had similar bias towards the Japanese before they sank all those battleship ships in Pearl Harbor.
-gb