There are always winners and losers at the same auction.
The same EXACT 1916-20 W-UNC Rogers Hornsby card graded PSA 6 sold in August of 2012 for $1,025 and then sold last night for $3,327.  Same AH, same card, almost the same description.  
 
Not sure what happened, but I'm not complaining...since it was my card!  
 
I concur with others that it is likely the perception that Green-Joyce cards are more plentiful than previously thought.  They're still pretty darn rare, so I'd say the price drop is staggering!
		
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http://imageevent.com/derekgranger
Working on the following:
HOF "Earliest" Collection (Ideal - Indiv):  250/346 (72.3%)
1914 T330-2 Piedmont Art Stamps......:  116/119 (97.5%)
Completed: 
1911 T332 Helmar Stamps (180/180)
1923 V100 Willard's Chocolate (180/180)