I don't know how they select IDB's but I might have an insight into max compensation offered. On checking in at JAX (To MAN via EWR and STR) earlier the screen gave the familar 'one or more of your flights may be overbooked etc'. It offered $150 or something equally derisory.
The GA was having to press the buttons for us (Passport check required) and I said not a chance when the message appeared. She then told us about the family of six at the next kiosk. Bumped off their flight. No more availability today or tomorrow on any carriers. They're each getting $988. Hire car to Orlando and a hotel overnight.
Strange amount I thought. As our flight is running late I checked FlightAware. Amongst the data it gives is the ticket range. The maximum for JAX to EWR is $988.
GA said they were already offering $500 comp to get volunteers for another flight but no-one was biting and they expected to have to pay $988 again.