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“We are clearly producing personalised, interactive knowledge at your fingertips at zero marginal cost,” he said.

Publishers are reaping massive profits from this model, charging hundreds of dollars for each digital textbook while their marginal costs remain negligible.

"Our country has the right to pay for electricity at the average cost of production and certainly not at the marginal cost of the latest gas-fired power plant in eastern Europe."

Other members of the supply chain such as farmers and growers or bakers, class about 70% of their costs as overheads, leaving marginal costs of around 30%.

“The marginal cost of funds for the U.S. banking system has just gone up a lot as a result of this flurry,” said William S. Demchak, the chief executive of PNC.