EjP wrote:

The most optimistic estimates I've heard for a Mars
mission put the price at about $500B.  Bush's "vision"
will get us there in a couple hundred years.

Then read the book "Mars Direct". The 500B price tag was for a massive
effort that would include refuel in space and carrying all the fuel for
both the journey out and lauch off the surface of Mars with them.

In Mars Direct the fuel is produced on Mars via some very simple chemistry
from the Martian atmosphere and a small nuclear generator.

Look, I'd be really excited to send a manned mission
to Mars, but you don't fund that with tax cuts.  It
would take a national goal (with national sacrifice)
and international collaboration on a scale that this
country is not capable of.

Well hows this for a thought - The US could have put a man on Mars for half
the cost of invading Iraq. Instead of dividing thw world, and diving it
into mistrust and dispair we could have been driving into a new age of
exploration and expansion. 

Here's an intelligence test. Bush's vision will:
   A.  Actually land a man on Mars
If you answered A, you're deluded.

Remember, for a tiny fraction of a manned mission
to Mars we could send unmanned probes to *every planet
in the solar system*.

The actual cost of putting a real mission to mars together is quite
manageable. Considering the staggering debt the US it seems to hardly
matter at all :)