You can get wireless headphones which aren't Bluetooth. I have a pair - Sennheiser HDR 120 II which I think have been replaced by the RS120. However, there is a compressor or automatic gain control (AGC) which adjusts the volume down, presumably to preserve one's hearing, and that does seem a bit strange. They're £100 which is expensive in my frame of reference (but not in @ped's, who is evidently rolling in it), but available second hand for half that.