Its a classic....your right about the Bing carbs. Pretty easy to rebuild, I would suspect the floats or seats are gone. Fork seals, unless you run gators, it's pretty common. I had a customer tell me once that they leak because of the bug skeletons carve grooves into the seals. (Never heard that one before).
Lot's of goodies included so that should justify the asking price.
If you have to get a Air Head...better be a RS!
Tomas
Here's one I service: As soon as this guy sells , I'm buying!