What am I missing about the 2010 and 2011 Shield Cent Proofs?

I see that the 2010 and 2011 Shield Cent PF70 Reds are going for around $130 while the PF70 Red 2009 Lincolns (set of four) are bringing about $60/each. Why are the Shield proof 70s bringing so much more?? Thanks for any info on this.
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WS
President, Racine Numismatic Society 2013-2014; Variety Resource Dimes; See 6/8/12 CDN for my article on Winged Liberty Dimes; Ebay