Suppose, for example, that a new, less expensive process (i. e., an improved recipe for production) is discovered after producers have already invested in machinery appropriate only to older methods. Although the new process would be cheaper if production were starting ab initio, it may be more profitable in the current situation to use the older machinery until it is depleted. That machinery may continue to have positive utility, even if that utility is now less than its original costs of production. Because those costs can no longer be recovered, they are irrelevant to any present decision regarding the use of the machinery. Paradoxically, the producers may be following the more efficient course by continuing to use the older process of production, even though that process may appear inefficient and obsolete to the superficial outside observer.