Why go to the moon again - been there, done that. Has to be Mars next. I'm in thorough agreement with the guy who said:
"If you're going to explore the world outside your home, which is more sensible - go somewhere far away or just walk around the block a few times then head back?"
As for the ISS, the problem there is that the damn thing was originally costed at $8 billion and is currently coming in at $400 billion because NASA have great technical skills but didn't hire accountants. Actually, they DID hire accountants - Arthur Andersen (yep - the Enron guys)...
Add to this the fact that ALL of NASAs policy decisions were based around the ISS - at the expense of other projects, and you begin to get a sense of why it costs so much. Hell, they even had to design new booster rockets to get the shuttle to the right orbit after they brought the Russians aboard - because for the Russians to be involved (a political decision - don't want any former Soviet rocket scientists taking their paycheck from Hussein or Bin Laden...) the station's orbit had to pass over Baikonur Aerodrome. This involves a higher orbit, so the shuttle needs more fuel. The cost of those boosters? $1 million. The tail begins to wag the dog...
As for a lunar colony - go for it, as long as no-one tries anything pathetic like annexing the whole chunk of rock as sovereign territory.
"That might have been the biggest mistake of my life..."
"It is unlikely. I predict there is scope for even greater mistakes in the future given your obvious talent for them."
Vila and Orac, Blake's Seven