Please read this page before purchasing sale items. It explains the general condition of yarns at different sale prices. Given this disclaimer, all purchases of sale items are final.
Yarns appearing on the sale page are there for several reasons. Mostly I need shelf space and these sale yarns are taking up the space I want to use. All of this yarn has been in a store for varying lengths of time, so it has been handled, may be missing its wrapper, or has generally been messed up from handling by customers.
Yarn up to 50% off is a current or recent yarn or colors that may be discontinued by the company, or didn't sell well and I want to clean out the whole line and replace with a more popular product. Most of these yarns are current to 5 years old, again on shop shelves for customers to look at and feel.
Yarn at $3.00/ball or more than 50% off is generally in excellent condition, could have been out of the bag but is nothing that I would hesitate to knit with to make a store sample or make up for my grandkids or for any charity knitting.
Yarn under $3.00/ball is probably very old. It may have a knitted square attached and might be missing labels. Some of the yarn may appear ratty, especially if the labels are off, it contains rayon, or is a slippery yarn. Some may be faded or dirty. Light colors do get dirty when stored or handled; that's a fact of life. Most blues, especially mid to dark blues and purples, fade in all kind of lighting.
I guess if you want a bargain, there are some risks involved. There are some excellently priced expensive yarns here and since I have written a disclaimer about these yarns, they are not returnable. In general I don't think you will be unhappy.