Jeez, on an annual basis, that Mars mission isn&#x27;t looking so bad!  That&#x27;s Apollo program money -- even less if you account for it in 1960s dollars.  My guess is that I&#x27;m personally not ever going to walk on Mars <i>or</i> drive through a hypothetical SR99 tunnel, so it&#x27;s largely a moot point.<p>Keep in mind that the Big Dig&#x27;s original cost estimate was something like $3 billion.  Turned out to be closer to $24 billion.  We&#x27;re not very good at these things, it seems.