To close the loop on this, I did some more digging myself using the litigation case files.
Ultimately, the actual value of the lost property was left to a private Appraisal Panel, which was established by six of the insurers, and the methodology employed by which was subject to appeals to the district court hearing the case. Here is a pretty informative yet non-technical account of their proceedings:
https://mdd.com/ce/pdf/insight_dec07_guestExpert.pdf
Since the appraisal panel functioned largely as a private arbitration, its proceedings themselves and its final determination remain confidential; however, a careful look at the record provides some clues as to where their determination landed.
The two attached documents are extracted form the docket of the SR Int'l Bus. Ins. case. They consist of a declaration and attachments thereto. In the second to last page of the second document, which contains attachments, you can find an excerpt from Silverstein Properties' claims from early on in 2002. At that time, Silverstein Properties was arguing that the total loss of the properties by itself (not including WTC 7) had amounted to $5.634 billion, and that lost business/rental value had already amounted to $671 million. (Neither of these figures includes clean-up or other ancillary costs incurred by Silverstein or the replacement cost of the towers or other buildings.) If we just extrapolate these figures out to take into account continued business losses going forward until the time of the final settlement in 2007, however, we are already at $9 billion in losses, not including clean-up and other ancillary losses or replacement costs or inflation.
As we know, Silverstein only wound up receiving $4.6 billion from its insurers for the losses (including the reduced $700 million in replacement costs), and he was obligated to pay to rebuild per his Port Authority lease. Estimates for the reconstruction costs all in run around $7 billion.
The port authority and various government agencies involved in clean-up and rebuilding may have ultimately ate some of the costs otherwise incurred by Silverstein Properties, but it looks like there was at least a $10+ billion loss to Silverstein Properties at the end of the day (and note the above does not take into account that, even at the time of the final insurance payments, One World Trade was not yet built and remained unoccupied until just last year, meaning Silverstein Properties was technically still losing business on some lost office space through that time).
Maybe Truthers will start calling him Unlucky Larry, as has always been more apt given that massive death, destruction, and loss were all thrust upon him suddenly by a group of madmen. To think he had to navigate all of that, all of the insurers, reinsurers, government agencies, etc., as well as harassment and defamation from Truthers, and he still managed to build an incredible new complex. NYC is lucky we had him in a position to use his expertise and Truthers should be embarrassed for shamelessly defaming him without even checking the available record.