gone

Radio stations do not broadcast anything above 15khz.

FM Radio and TV audio have a 15KHz audio bandwidth. The stereo subcarrier is above this.
AM has a 5KHz bandwidth.

thats output at what? 19 khz?

In FM radio, the pilot tone is at 19KHz (half the subcarrier frequency)
For MTS TV sound, the pilot is at the horizontal frequency, 15.734 KHz, the stereo subcarrier is twice that. SAP is on a subcarrier at 5 X Fh, and the Pro channel as at 7 X Fh.
The lower frequency limit is 50Hz.

AM is more than 5khz, it's actually 10khz, but not many receivers are capable of this. most are cut at 5khz, and most car radios (to cut down on alternator noise) cut it at 3khz. Most stations, to play nice with adjacents set their processors to cut at 5khz anyways, just so they don't overlap too much. (they also know that a receiver hasn't been made in 20 years capable of 10khz anyways)

Thought I read somewhere the low end "spec" is 40Hz for FM and 50Hz for AM.

AM is more than 5khz, it's actually 10khz, but not many receivers are capable of this. most are cut at 5khz, and most car radios (to cut down on alternator noise) cut it at 3khz. Most stations, to play nice with adjacents set their processors to cut at 5khz anyways, just so they don't overlap too much. (they also know that a receiver hasn't been made in 20 years capable of 10khz anyways) the bandwidth of a stations transmission and the bandwidth of the space between them is set by the fcc and not a decision left to the station.

Radio still sounds incredible, though.