Consultation materials:
http://pastebin.com/raw.php?i=3heUAyVD
http://pastebin.com/raw.php?i=x9yS8Fk9

Notice the six 500 XBT outgoing transactions. Conceivably, one could have been from the only who deposited more than 500 XBT (Bitscalper's lifetime was too short), so this leaves 2500 XBT unaccounted for. Subtracting from this bitscalper's "admin" account of 1142.74540194 gives a lower bound of 1350.10259806 XBT.

It should be noted that this is a conservative estimate.