[1] : http://en.wikipedia.org/wiki/Apollo_program#Program_cost
Either terraforming mars or we might make it to Alpha Centauri by the next century.
> In 2009, NASA held a symposium on project costs which presented an estimate of the Apollo program costs in 2005 dollars as roughly $170 billion.
So multiply by nine then.
[1] : http://en.wikipedia.org/wiki/Apollo_program#Program_cost