A basic feature of the utility function (demand curve) is the
law of diminishing marginal utility. That is, as a person consumes
an item or a product, the satisfaction or utility that they derive
from the product wanes as they consume more and more of that
product. In other words, the price a person is willing to pay (or
the demand) for that product decreases with consumption. However,
our demand for some environmental goods (e.g., clean air/water)
does not wane...