不怕不识货，就怕货比货

bù pà bù shí huò , jiù pà huò bǐ huòbupabushihuo,jiupahuobihuo

1. lit. don't worry about not knowing goods, but about comparing them (proverb)
2. fig. goods' (or person's) true value can only be determined through comparison

Study it in Yanamino