Except there is, a negotiation is based on the next best alternative; which is the legal system.

Mcks wouldn’t have settled for that much if they thought they’d fare better in court.

They didn't want it in court because it would have made a documented legal precedent around liability.

"One former partner called the settlement hugely significant because it shatters the distance that McKinsey — which argues that it only makes recommendations — puts between its advice and its clients’ actions. For decades, the firm has avoided legal liability for high-profile failures of some clients, including the energy company Enron and Swissair, Switzerland’s defunct national airline."

https://www.nytimes.com/2021/02/03/business/mckinsey-opioids...

1. I think that’s making a guess into their intentions which we’re not qualified to do

2. Even if we take #1 for granted, the $500MM figure is still based on something. The counter-party could’ve settled for $100MM or insisted on $1B but they reached that number for a reason.