As of the year end of their last 990 filing (3/31/2011):
Cash: 1,142,102
Savings & Temp Investments: 7,023,626
Accounts Receivable, net: 4,608,225
Inventory: 96,828
Prepaids: 662,921
Land, Buildings, equip: 7,376,710
Accum Depreciation: 6,522,426
Investments - Publicly traded: 24,597,862
Investments - Other: 2,231,901
Total: 41,217,749
Accounts Payable: 6,196,427
Deferred Revenue: 17,519,618
Total: 23,716,045
Unrestricted Net Assets: 17,009,040
Temporarily Restriced Net Assets: 492,664
Total Net Assets: 17,501,704
If you look at their publicly available 990 it has details on the costs and revenues related to the marathon. I'm just way too lazy to type it all here. I'm sure many of the expenses are already paid for and aren't refundable. But I would guess this is where an insurance would hopefully come in for them.