"We are back from the edge of the abyss," U.S. Treasury Secretary Timothy Geithner declared last week, nearly a year after the collapse of financial titan Lehman Brothers Holdings Inc. (LEHMQ) sent global market confidence plumbing new depths.

Since then, unprecedented interventions by the U.S. government have helped to calm markets and stabilize the financial system. But they haven't come without a cost.

The final tally for taxpayers could reach well into the hundreds of billions of dollars or more, depending in large part on how much the government can recoup from its various investments in beleaguered firms. Markets also remain fragile, leaving open the possibility of future interventions adding to the taxpayer tab.

A week before Lehman collapsed on Sept. 14, 2008, becoming the biggest corporate bankruptcy in U.S. history, officials seized mortgage giants Fannie Mae (FNM) and Freddie Mac (FRE). They agreed to pump $200 billion of capital into the firms to keep them solvent in return for preferred stakes in both.

The Treasury Department has since doubled its commitment to $400 billion and injected around $96 billion of taxpayer aid into the companies to plug their mounting credit losses. It will be a challenge to recoup that money as well as future capital infusions that are likely to occur, Karen Petrou of Federal Financial Analytics argued.

"I don't think we're in any respect done funneling funds into Fannie and Freddie," she said.

Meanwhile, the Federal Reserve's balance sheet has more than doubled to more than $2 trillion since last year due to the Fed's various interventions in the financial system.

To quell the market panic, the Fed stepped in to prevent investors from fleeing money-market mutual funds and backstopped lending to industrial companies. It also spent billions of dollars to keep credit flowing to home buyers and people needing auto and student loans. More recently, it began supporting lending to the commercial real estate market.

The Fed also agreed to provide insurance giant American International Group Inc. (AIG) an $85 billion loan, which was later reduced to $60 billion. Earlier last year, it had guaranteed nearly $30 billion of failed investment bank Bear Stearns Cos.' assets to facilitate its sale to JPMorgan Chase & Co. (JPM).

In testimony before Congress in July, Federal Reserve Chairman Ben Bernanke suggested the AIG and Bear Stearns investments were losing money, describing them as "a little bit under water." But he said the Fed was making "a nice profit" on its lending and other emergency programs. Just how much money the Fed ultimately recoups from the programs will depend in large part on the strength of the collateral underpinning the loans.

Taxpayers risk exposure to some losses under the Federal Deposit Insurance Corp.'s program to guarantee bank debt, set up to get banks lending to each other again. All told, there have been 92 bank failures in 2009.

Then there's the $700 billion Troubled Asset Relief Program authorized by Congress, used to recapitalize banks, prop up the U.S. auto sector and help troubled homeowners to avoid foreclosures.

Along with the Fed, the Treasury has committed up to around $180 billion of funds to rescue AIG. Treasury also pumped $20 billion each into Bank of America Corp. (BAC) and Citigroup Inc. (C), agreeing along with the FDIC to guarantee roughly $300 billion of Citi's bad assets.

In perhaps its most controversial move, the Treasury sunk $81 billion into General Motors Co. and Chrysler Group LLC. The congressional panel overseeing TARP recently concluded that taxpayers are unlikely to recoup all these funds.

The Treasury's uses of TARP funds have spurred a public backlash against federal bailouts and have exacerbated concern about the federal deficit.

"I think that many Americans share a fear that I have that an emergency piece of legislation that was meant for economic stability has now morphed into essentially a $700 billion revolving bailout fund for the administration," Rep. Jeb Hensarling, R-Texas, said last week.

The administration has defended its use of the TARP funds, pointing to stabilizing markets. Geithner said last week that the administration no longer believes it will need another allotment of rescue funds.

The Treasury expects it will get a portion of the funds returned as banks exit the TARP program and repurchase government warrants on their stock. So far, the Treasury has recouped around $70 billion of the $204 billion it has injected into the banking system.

-By Jessica Holzer, Dow Jones Newswires; 202-862-9228; jessica.holzer@dowjones.com