Vox is arguing that the FAA's own guidebook says $1350, not $800, and that it's up to the airline to negotiate more. The problems are
1) Nobody is flying Chicago to Louisville on a Sunday evening for fun
2) People flying Chicago to Louisville on a Sunday evening do it regularly
3) People who fly that leg regularly have a pretty good idea how delayed, shitty and overbooked United tends to be on that leg
4) People with an idea of how shitty and overbooked United tends to be have probably gotten worthless vouchers before
5) People who have gotten worthless vouchers before are not eager to get more worthless vouchers
6) It boggles the mind that a paying customer could be forcefully removed from a flight because United couldn't solve their bullshit crew problems.
This is a flight full of people going "there's no way United could be that shitty" and a country full of people going "wow. United is shitty."