蘿蔔快了不洗泥 [萝卜－－－－－]

Jyutping
Pinyin luó bo kuài le bù xǐ ní

Definitions (CC-CEDICT)

when radishes are selling fast, one doesn't take the time to wash the soil off them (idiom)
fig. when business is booming, merchants tend to offer goods of inferior quality