I think a big part of the, "why aren't we going to the moon anymore" question can be answered by another simple question...
why bother? We've been there, done that took the samples done the test, left foot prints, and a load of junk there...
whats the point in spending a load of money to send others there to repeat whats already been done.
I think a manned mission to mars will be a long long way off...
IMHO a new launch platform has to be made first,(something like an international space station?!?)...
at present on of the biggest costs is actually getting outside of the eraths atmosphere. in a rocket...
however space shuttle can be launched from the back of high altitude aircraft etc... maybe once the costs have gone down they'll start sending people off to the stars?