noun
law of one price
Economic principle stating that identical goods should sell for the same price in different markets when expressed in a common currency, assuming no transportation costs or trade barriers.
一物一価の法則が成り立つには、取引費用が無視できるほど小さい必要がある。
For the law of one price to hold, transaction costs must be negligibly small.
購買力平価 (purchasing power parity) is a related concept that extends the law of one price to a basket of goods, comparing overall price levels between countries.
Compound of 一物 (one good), 一価 (one price), and 法則 (law). The term is a direct translation of the English 'law of one price'.