Howl time!!

I just heard a radio announcer say: "Gas prices in the D.C. area are a dollar cheaper [sic] than they were...."

I wish someone would inform this person that prices are not cheaper. Prices are lower. (Goods or services are cheaper.) Why does this minor mistake annoy me? Mostly, I think, because it represents a small instance of a larger phenomenon: presumably educated, intelligent people making basic English mistakes on the airwaves every day. This is not about informality or slang or colloquialisms, which I have nothing against. It's about locutions that are obviously, patently wrong. I know that languages evolve and all that, and I know no one is perfect, but it's getting to the point where formation of a Committee for the Defense of English would not be an irrational response.

If you don't like this post or think there are errors in it, please howl in the comments.