At the Washington Arms Collectors gun shows here in Washington state, you must be a member (background checked) and are supposed to only sell to another member (who is also background checked). If you are caught selling to a non-member, you are kicked out of the gun show (I think for life).
A collector show is a bit of a different animal than a public gun show. As you noted the attendees are known actors who have already submitted to a background check. C&R license holders are much the same. A C&R can buy any C&R gun, even a handgun, without paperwork or submitting to a waiting period.