Hi gbaikie,

The most oft-quoted pricetag for Mir was $4.3 billion. That's just to build it (not sure if it includes the cost for putting it into orbit). Then you got to have the infrastructure to support it, both with round-the-clock ground control and monitoring, satellites, relay stations, and frequent resupply flights, which the Russians have quoted as $250 million per year. It was up there for 12 years... $7 billion total.

Any way you cut it, $7B is no small chunk of change. :-)

Based on that, I think that building and then maintaining a moon base, even a modest one, would cost far more than $10B.