C404 Trap!
Although the merchant selling the jade was somewhat unscrupulous, the stone itself was invaluable.
If someone falls in love with a stone, even if it's riddled with flaws and impurities, to them, it's a treasure beyond price.
Conversely, if someone dislikes a stone, it could be the finest jade and still hold no value to them.
Lee Zhanmu observed this and thought himself quite impressive