Why Amateur FM on VHF repeaters uses about 5 kHz peak deviation with audio out to roughly 3 kHz, and Carson's rule (bandwidth = 2 x (deviation + highest audio frequency)) gives about 16 kHz, so the usual figure quoted is 10 to 15 kHz. That is why repeater channels are spaced 15 or 20 kHz apart. FM is much wider than SSB voice (about 3 kHz) because the carrier swings back and forth in frequency.
Watch out The choice near 150 kHz describes commercial broadcast FM, which uses much larger deviation and 200 kHz channel spacing; the under 500 Hz figure is a CW signal.
Ham FM fits a 15 kHz repeater channel; broadcast FM needs 150 kHz. Same mode, ten times the room.
Ham FM is a young teen: 10 to 15 kHz wide. Add a zero and you have broadcast FM, which is the trap.