expression, i-adjective
keenly aware of one's own interests; shrewd about personal gain
Describes someone who is quick to notice and act on opportunities for personal benefit, often with a slightly negative connotation of being calculating or self-serving.
彼は利にさとい男で、儲け話にはすぐ飛びつく。
He's a man who is keenly aware of his own interests and jumps at any money-making opportunity.
利にさとい人は、損得をすぐ計算する。
People who are shrewd about personal gain quickly calculate profit and loss.
Means 'sharp, shrewd, not missing a trick' and is more general, while 利にさとい specifically focuses on being alert to one's own financial or personal advantage.
Means 'calculating, mercenary' and has a stronger negative nuance of coldly weighing benefits, whereas 利にさとい can be more neutral, simply describing a keen sense of self-interest.
Phrase composed of 利 (り, 'profit, advantage') + に + さとい (聡い/敏い, 'sharp, perceptive'). The exact historical derivation is uncertain, but it follows a common pattern of using に to mark the area in which one is perceptive.