代金
だいきん · daikin · JLPT N3 · noun
monetary value
💴 代金 = in exchange for + money: the money you hand over for something
代 means to replace or stand in for, as in 代わり (substitute). 金 is gold or money. So 代金 is the money that takes the place of the goods: the price you pay. It also shows up in 代金引換, cash on delivery.
代 — person radical 亻 + 弋 (stake/dart, phonetic)
代 is a semantic-phonetic compound: 亻 (person) gives the meaning and 弋 supplies the sound. The original sense was one person taking the place of another, which broadened to 'substitute,' 'replace,' and then 'generation' or 'era' — successive groups of people replacing the previous.
金 — roof 亼 + two dots (metal nuggets) + earth 土
Originally a pictograph of metal nuggets buried in the earth beneath a covering, with the two dots representing pieces of ore. It first meant 'metal' broadly, then narrowed to 'gold' as the most precious metal, and by extension 'money'.