Plain and simple United violated their contract with this man, and the government stepped in and enthusiastically used the only tool in their bag, violence, to enforce United's violation of the contract. This man should be set for life after the lawsuit.
The contract states an action "deny boarding", the flight was already completely boarded.
The contract states a condition "oversold", the flight was not oversold.
The contract also states a priority or ranking (fare class, elite status, etc.) for which individuals will be chosen to "deny boarding" (note, not remove from aircraft). This man seems to have been chosen at random.
The only legal option United had was to keep sweetening their offer for volunteers until they had their 4 seats for crew... Or seek alternative transportation for their crew, or find an alternate crew for the next flight so they could get their employees where they needed to be on their own aircraft.
As for my price... I only travel commercial air for work as I will not have my rights violated and be sexually assaulted for a vacation. So typically if I'm outbound I need to be at my destination to work, small delays I can work with but not being on site the first day could make the trip a waste. Maybe $3k and getting bumped to the top elite status for a year with lounge access included, or $5k without the perks, and even then only assuming I could make it work to not be on site at my originally planned time which is sometimes the case but not always. For a return flight (typically much more flexible the next few days), $1k and some perks or $2k with no perks.