The TENS unit my insurance supplied me with was worth about $800. My TENS/IF stim is worth about $1500. Those babies can be really expensive, but from an insurance company's point of view they are cheaper than surgery and cheaper than Remicade and cheaper than treating serious side effects from meds and cheaper than a whole bunch of other stuff. I love my TENS. It has been a lifesaver for me at times. My IF stim was also a big help in calming down my neck.
Not everyone finds them so helpful, but they sure have been for me.
Kare