Some Chanel goes on sale, but the SA won't know until they get the paper work telling them what is and what isn't on sale. It's never much of a discount and it's usually only 1/3 off. Even then, the place is crazy with customers.
By the way, I've seen items go on sale and when the sale is over, the item is right back at its regular price. The SA will not mark it down again... because they can't. The Head Office is very intolerant/unforgiving that way.