1 Vernon Jackson-sales analysis 5-1-2011

as per street easy the building has 8 unit sold and Recorded. can someone give a explanation on difference in price per square foot unit # date sold $ s/f $$pf ter/bal room 2A 3/18/2011 $559,000.00 752 743.35 367 1+1 2B 3/18/2011 $440,000.00 600 733.33 0 1+1 4B 4/5/2011 $520,326.00 600 867.21 0 1+1 3C 3/22/2011 $752,487.00 991 759.32 174 2+2 3D 4/5/2011 $405,600.00 505 803.17 0 1+1 2E 4/5/2011 $425,880.00 599 710.98 0 1+1 4E 3/14/2011 $445,000.00 599 742.90 62B 1+1 4F 4/4/2011 $463,398.00 576 0.00 79B 1+1 why is 2b sold for $733 ppsf and 4b sold for $867 ppsf?