Last year I picked up a starter kit with a WLF, 120 back, 90mm lens, and Pro-S body, all in Excellent condition, for $320 from KEH. I noted a few weeks ago that similar sets on KEH were closer to $350. (Note that KEH had my system listed as "Bargain" condition, but as so often happens with KEH, their Bargain condition is much better than expected.)
Getting $600 for the setup listed is going to be a stretch unless you can find a collector. Users don't care if the body has had 10 rolls or 100 rolls through the camera, because an RB will go far, far beyond 100 rolls without problems.
So if you want to collect the camera, $600 is fine. If you want to use the camera, the one listed here on APUG is a much better deal. Or check KEH...many of us have purchased "Bargain" condition items from them and gotten equipment that looks fairly new.
I'll second Dave's comment on bargain condition items from keh. I've purchased a rb67 body and back, 2 lenses and a metered prism, all in "bargain" condition and they are in great shape, all for quite a bit less than $600