The AS language is clear, the passenger has accepted it and a chargeback dispute will fail. Since at least 2014, DOT has not touched these claims and some of them are much more stark in terms of amount.

While I hate to depend on customer service gestures because they can be lousy, they are sometime decent, especially if you regularly use the carrier. But, once you've gone down the dispute & DOT path, the customer service team is out of the picture. So, while there is no economic cost to filing these complaints (although some card issuers do track denied chargebacks as a customer value metric), there may be indirect costs in doing so.