For example, an unpolluted environment (and, say, lesiure) could be regarded as a commodity which had to be traded off with other commoidities (the opportunity cost).

• 但奥国学派及芝加哥学派则重视 "不完全讯息"，所以反对计划经济。但不论赞成或反对，都不涉及 "价值判断"。