MountsPro offers the Universal HDTV Wire Mount for $29.95 with free shipping. That's $10 under our mention of a similar mount from yesterday and is among the lowest total prices we could find for such a mount. This mount adjusts to suit a wide range of flat-screen displays up to 100 lbs.
Update: Overstock.com offers a very similar mount for $19.99 plus $2.95 for shipping. It accommodates HDTVs weighing up to 110 lbs.