These are a nice, inexpensive way to help boost your CHA when selling to or buying from merchants. I've been carrying a pack full of CHA gear for a long time and it has more than paid for itself. My base CHA is 50 (I play a halfling) but with my CHA gear on it reaches 109. With indifferent or better faction that gets me the best prices available from most vendors.
In my experience a CHA over about 100 is all you need for this.
Other good CHA kit items include gold catseye bracelets, a crude stein, and split paw necklaces. Some of the guards on the wall in Misty Thicket drop a ring that adds 5 to CHA. Halflings can quest for a Leatherfoot Raiders Skullcap that also adds to CHA.