They're often valuable for vastly different reasons â like the World War II-era coins minted from atypical metals, or double-printed pennies â but each one is easy to miss if you're not paying attention. See also: Californian Couple Finds $10 Million Worth of Gold Coins in Tin Can.
A subsistence economy is a non-monetary economy which relies on natural resources to provide for basic needs, through hunting, gathering, and subsistence agriculture.
However, despite the primacy of self-sufficiency in subsistence farming, today most subsistence farmers also participate in trade to some degree, though usually it is for goods that are not necessary for survival, and may include sugar, iron roofing sheets, bicycles, used clothing, and so forth.