Some people are claiming that all spaceflight knowledge in this country has been lost and it would cost far more (in constant dollars?) to re-do what was done in the 60's to get us to the moon. I'm not so sure.
I'm working in an engineering field (not rocket science) which was dominated by experimentation/prototyping when it was "hot" (WWII and shortly thereafter). Giant teams of people (100s or more) would be doing what our very small team is today (3-ish).
Granted, we have their shoulders to stand on, but instead of doing a WHOLE LOT of prototypes, we run supercomputer simulations and "try out" thousands of designs. And when we build them, they work--the first time.
I would say we re-do (sort of, actually we're pushing today's technological boundaries) the equivalent of what our fathers and grandfathers had done, faster, cheaper, better, and with stupider, less-skilled people (I'm including myself) --because we have better tools to extend our minds and bodies with today.
So I am not so sure that re-engineering the Apollo program would cost anything like the original development program. I think it would depend on what kind of modeling tools and other tech developments are available now that didn't exist then.
What's more, we're currently executing what I would call an "archaeology" project, reviving a 40-year-old design. The existing documentation is lacking, but it's still helping us a lot--we'll probably get this thing built for 1/10th the cost "back when" thanks to what our ancestors have left us and thanks to the tools we have today. And we might even build it better than they could ever have done, thanks to being able to use supercomputers to search for an optimal design.... But that remains to be seen.