buy the case (/casket)and return the pearls (/jewels) —be ignorant of the value of a thing; show lack of judgement; make the wrong choice
❍ 不善读书者，昧菁英而矜糟粕。～，虽多奚益？(裘廷梁 《论白话为维新之本》) Those who do not know how to read fail to see the essence but talk big of the dross. Such lack of judgement is just like buying the casket and returning the pearls to the sellers. What use is there reading a lot like that?
买椟还珠mai du huan zhu
keep the glittering casket and give back the pearls—show lack of judgement
买椟还珠mǎi dú huán zhū
椟：木匣子；还：交还；珠：珍珠。买下木匣子，却又把里面装的珍珠还给人家。比喻没有眼光，取舍不当。show lack of judgement, make the wrong choice