Data point. I've been checking every 5-7 days just when I'm bored on my phone. Had been consistently $800+ (also stating: Only 1 seat left at this price!) for the last few weeks. I just checked right now and it dropped to $503, so I booked it using Chase UR (28k) plus $69. The entire cabin was unbooked and no seats had been sold. This is for a weekday 2:50 PM SAN-BOS flight.