National treasure can be an asset, which may or may not have monetary value.
Gu Ae Jung used to be a household name in a popular girl group called National Treasure Girls or Kukbosonyeo (KBSN; 국보소녀). Even when they disbanded, she never stopped being a part of it. Her ringtone, her autograph and the posters are all still related to the group. National Treasure Girls was her love and something she always held close to her heart. Until Dokko Jin comes along and rises to the highest height of his popularity making him the current National Treasure. Conversely, Gu Ae Jung sinks to the bottom after the disbandment of KBSN and the exposure of several scandals in the media.
National Treasure is also used as way for Yoon Pil Joo to describe how he feels about Gu Ae Jung. Things did not go smoothly when they first met. Gu Ae Jung mistakenly went into his room thinking that he was PD that was going to offer her a new gig. He thought she was a new doctor he was looking to hire. When he asked about her skills and how much she’s worth, she thought he was looking to sleep with her. Angry, she yells that she can’t be bought and because she was a KBSN member making her a national treasure. He brings this up again later when he comforts Gu Ae Jung after a bad encounter with Dokko Jin. Pil Joo reminds her about the national treasure comment when they first met. He says that he couldn’t do anything when the number one nation’s treasure (meaning the Namdaemun gate that was burned down in 2008) was hurt but when the National Treasure in front of him is hurt, he’d heal her.