I used the therabite religiously, and I have benefitted from it. I still do my jaw-opening exercises now, without the device, but I had to use it at first and shudder to think that without it I wouldn't be able to open my mouth now enough to insert a spoon!
Cheap it is not. It costs about $450 over the internet, and about $650 to your insurance company. Mine was prescribed by my dr., so it was covered by the insurance. You can order new bite pads for it, and they are cheap, but the device is not.