How is the passenger unreasonable at all. United could have easily avoided the situation by paying the market price for a seat, they didn't even offer the maximum they could have per their own contract.

I'm sure someone would have opted to delay their lives if the offer was $1k, $2k, hell $3k. Why does United get to economically benefit by getting their pilots to the next flight and profit from it, while inconveniencing someone else who has already purchased the flight? Sure, they're legally allowed to do what they did, but they didn't even bother to offer the maximum amount their own contract says to, so not sure why they would get any sympathy.