mek - I hear you - I'm trying to remember how much my splint was when I got it a long time ago but I think it was about $800. The night splint was $500. My TMJ never gave me a total of how much it would cost long term - I don't see how they predict this outside of a base set amount to cover splint, xrays, MRI, etc. The ongoing costs of TENS, injections, etc., is unpredictable especially if the case is a chronic one.
In my case I've surpassed the designated set amount from insurance by a long shot, so I'm responsible for the $$$ out of pocket because the insurance coverage isn't great at all for TMJ.