expression
a beautiful woman's smile is worth a thousand pieces of gold; enchanting smile of a glamorous woman
A yojijukugo (four-character idiom) used to praise the captivating smile of a beautiful woman, implying it is priceless. Literary and somewhat old-fashioned; not used in everyday conversation.
彼女の笑顔はまさに一笑千金だ。
Her smile is truly worth a thousand pieces of gold.
From Chinese classical literature, combining 一笑 (one smile) and 千金 (a thousand pieces of gold). The exact origin is uncertain, but it reflects the high value placed on a beautiful woman's smile.