It is the rate of change in total utility per unit change in quantity and is not the utility of a marginal unit.

它是（商品）量的每单位变动带来的总效用变动率，而不是边际单位的效用。

youdao

The prof's New Economy spin was that frictional diminishing returns did not apply to software or Internet firms because of their tiny marginal unit costs.

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Or if you prefer, the marginal cost of one more unit of production is near zero.

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To fund those lawyers and keep Skyhook at least in marginal growth, Morgan is chasing what he calls a 2-billion unit market for digital cameras and e-books.

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