One more thought on used parts...
If I remember correctly, those hearing aids that we send back for credit
aren't totally trashed. Many of the parts go back into a hearing aid that
has been sent in for repair. So when you send in your 2 week old hearing
aid in for repair because the receiver fizzled out, you may get a 3 month
old receiver that has been in an ear full of cheese. Those used parts are
keeping the already outrageous prices down a bit.
If the manufacturer had to notify if a used part was put in, it would only
be fair to let them label how used. It would get pretty difficult.