The cost of extraction would be higher than the value of the copper to us.

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The only pristine rainforests are those which are simply inaccessible because of steep topography or the cost of extraction and transport to the coast.

BBC: Why the West should put money in the trees

Human societies will thus continue to search for new sources of water, but the cost of procuring water is a function of the combined cost of extraction, harvesting, transportation, treatment, storage, and delivery.

UNESCO: Natural Sciences

While the company is among the higher-cost operators in its gold extraction activities, its silver bi-product sales reduce the net cost to among the lowest in the industry.

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Establish a system of carbon taxes on all fossil fuels, to begin to reflect the real environmental cost of their extraction and use.

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For BP Amoco's soft-spoken CEO, Sir John Browne, deep water offers the prospect of the largest untapped reserves and the lowest-cost means of extraction.

FORBES: Going deep

He admits that it is not simple to pull the sugars out of non-food material like pulp or wood waste, but says that even factoring in the extraction process, the final cost should be lower than using corn starch or sugar cane, both of which are much higher-priced commodities.

FORBES: Cobalt Technologies Pushes The Green Chemical Envelope

There is a huge qualitative difference between an economy built on natural resource extraction, where the populace is a cost center, and an economy built on productive labor by the population, where increasing capabilities of the society leads to more wealth.

FORBES: Why Have The Islamic Countries Failed To Develop Even With Resources Like Oil, While Countries With No Resources Like Switzerland Have Flourished?

Firms that had used unrealistically low cost estimates for extracting oil from ageing fields have suddenly been bailed out of trouble by the price rise, which makes extraction viable, and thus reserves proved, even at a higher cost.

ECONOMIST: Oil companies

Before the Chinese restrictions on exports the La and Ce were often selling at a discount to production cost: for they were simply by-products of the extraction of the more desirable and more expensive elements.

FORBES: The Coming Glut of Rare Earths