How do you feel about some stores charging extra for "extended" sizes of clothing?

I’ve noticed several stores practicing this lately. For example, I was just browsing Alloy and noticed that for their jeans, they list a price range rather than just a single price for the pair of jeans. Any size 15 and up is more expensive than the smaller sizes. They call these sizes “extended sizes” and charge about four dollars more than the “regular sizes”. They do this with some of their tops as well. I’ve seen this at several stores, this is just one example.

While this policy doesn’t affect me at all, I do find it a bit strange that some stores choose to follow it. What’s your opinion on this pricing method? Why do some stores choose to do this, while most don’t? How do you feel about them calling it “extended size” rather than “plus size” or something else?