cost

From Latin cōnstāre (con- 'together' + stāre 'stand') — literally 'to stand together / stand firm,' which came to mean 'to stand at a price.' What a thing 'stands at' is what it costs. Through Old French coster it became English cost (price, expense, the price you pay in money or in suffering), costly (standing at a high price), and the modern compound cost-effective (worth what it costs). The same cōnstāre also gives English constant and constancy — 'standing firm = unchanging.'