Overwhelmingly, agencies are compensated by charging their clients a fee, estimating labor cost and including an agreed profit margin.

FORBES: Coca-Cola Is Changing The Way It Pays Agencies

The Office of Reconstruction and Humanitarian Assistance has only just begun the task of estimating the cost of post-war humanitarian assistance.

CENTERFORSECURITYPOLICY: Post-War Planning

Airlines now have to carry mileage liability at the "fair value" of what the award credits could be sold for, instead of estimating the cost in fuel and service to give away otherwise empty seats.

WSJ: Saving Frequent-Flier Miles From the Ax

"The existing deficiencies in management structure, institutional culture, cost estimating and program control must be acknowledged and corrected for the program to move forward in a credible fashion, " it said.

BBC: Nasa in dock for overspending

It justified the cost by estimating annual river traffic of 12 million tons.

FORBES: A river of subsidies

Chrysler capped off its best October in five years, with sales rising 10% despite the three-day disruption of Hurricane Sandy. (Ford, for example, despite estimating that the storm cost the industry 20, 000 to 25, 000 sales, reported a small sales increase.) With gas prices declining and consumer sentiment rising, experts expect automotive manufacturers to experience gains into 2013.

FORBES: Is Manufacturing Making A Comeback In The U.S.?

Estimating how much it will cost to convert to the euro is far from easy.

BBC: How the euro affects you

There is a large element of guesswork estimating the bill's cost.

FORBES: Magazine Article

"You rarely see a decorator at Home Depot, " he said, estimating that at least 40% of the cost of a house is spent on interior surfaces.

WSJ: A Silicon Valley Contractor Spills His Secrets

The discrepancy between the original cost and the actual cost came in part because contractors originally were "overly ambitious" when estimating the project, Fischer said.

CNN: FBI turns on new crime-fighting system