There's an indirect effect on the 'hot' cards of the day and on very expensive cards. It doesn't take many buyers sitting out the auctions to lower the results on marquee stuff. Though I am guessing that some of the pullback on mega-priced postwar stuff is a result of the collapse of the shilling ring that was working over the postwar market through PWCC and other outlets. But we needn't get into that again
One thing I noticed during the downturn was that collectors who are into lower grade and inexpensive stuff didn't pull back the way others did. Every show I attended had plenty of action at the cheap card tables and dollar boxes while expensive stuff sat. Turns out collectors don't lose the bug even if things look bad, they just channel it into cheaper endeavors.