In an earlier post, I discussed the wastefulness of manned spaceflight. In particular, plans to return to the Moon or go to Mars cannot be justified in any sensible cost-benefit analysis. The cost is high, and the main benefit seems to be national prestige. Human spaceflight is essentially defended in a circular way: we need to undertake it so that we can learn how human beings function in space.
A post on Gristmill captures it well:
Let me be clear. There is a 0 percent chance that this Moon base or anything like it will ever be built, for the following reason: the moon missions in the ’60s and early ’70s cost something like $100 billion in today’s dollars. There is no way that setting up a semipermanent lunar base will be anything other than many times more expensive. That would put the total cost at one to a few trillion dollars.
Assuming that this taxpayer money needs to be lavished on big aerospace firms like Lockheed anyhow, it would be much better spent on satellites for the study of our planet (Some comprehensive temperature data for Antarctica, perhaps? Some RADAR analysis of the Greenland icecap? Some salaries for people studying climatic feedbacks?) or on robotic missions to objects of interest in the solar system.