1. What does it mean?
Short for 가격 대비 성능의 비율, the relationship between price and performance. In everyday reviews, 가성비가 좋다 means that a product or service offers good practical value for what it costs.
Also written or said as value for money
2. The nuance
Cheap does not automatically mean good value. A more expensive item can still have good 가성비 if its usefulness justifies the price. Unlike 가심비, the emphasis is on practical return rather than personal delight.
3. Examples
“이 이어폰은 가격에 비해 소리가 좋아서 가성비가 괜찮아.”
These earphones sound good for the price, so they're decent value for money.
“가장 싼 것보다 오래 쓸 수 있는 게 가성비가 나을 수도 있어.”
Something that lasts longer can be better value than the cheapest option.
Sources
Korea Policy Briefing: language and culture
References support the meaning and usage. Example sentences are written for NoCapWiki.