dont anyhow hor, u must know market price.
my previous trip one month ago i went in to some spectacle shops to ssrr, no matter is big store w many branches or shops in Ximending street corner, the pricing also chop carrot one.
got one big store named 年輕人眼鏡, i see their rayban priced until $400-500 SGD,
if u go queensway or peninsula, rayban (authentic) are priced ard $170- 250 SGD.