(CNN) On Thursday it was announced that United Airlines had reached an undisclosed settlement with Dr. David Dao, the passenger dragged off a flight just a few weeks ago, bloodied and semiconscious, and seen in a video that generated a flood of negative publicity for the airline.

It must have been a kajillion dollars, right?

Not necessarily.

Although, according to Dao's attorney , he suffered a concussion, a broken nose, injuries to his sinuses requiring surgery and lost two front teeth, the most significant question in terms of assessing damages is whether he will suffer long-term health consequences.

Valuing a plaintiff's injuries is not an exact science. No two cases are identical. If you strip away the disturbing viral video of Dao's ordeal, and evaluate the case strictly by his injuries only, this case might not have had a lot of monetary value for the plaintiff in case of a trial.

What about the embarrassment of being watched by millions of people? Doesn't that have value? It does. In assault cases , a jury can consider the humiliation and indignity suffered by the plaintiff and compensate him. The thing about these damages is that they are uncertain, and hard to value.

In the weeks following the Dao video, there were some who thought Dao should have just gotten off the plane . If some of those voices found their way onto a jury, they might not have awarded Dao much for embarrassment. In fact, some might have foisted some blame onto Dao for not disembarking willingly.

In injury cases like this, quantifiable medical injuries are normally the primary factor in assessing value. Indeed, Dao sustained medical injuries, but the extent of them may not be the kinds that are likely to produce a significant payout.

Broken teeth are certainly painful, but that period of pain could be limited to the time between the injury and when the dentist fixes them. The price of those teeth is also an ascertainable amount. Ten thousand dollars might be a reasonable value of some dental implants, but it's the kind of injury that is largely fixed once the procedure is over. Similarly, a broken nose that heals on its own is painful, but probably not for the rest of one's life.

The real driver in high damage awards in personal injury cases is long-term pain or impairment. For example, herniated discs and torn rotator cuffs are not gruesome, obvious injuries, like broken teeth or noses. Yet, they can lead to long-term treatment and surgeries, permanent disability and a lifetime of pain.

His concussion is probably the injury with the most potential damages—or least. Some concussions are hard to even diagnose . A concussion is considered a mild traumatic brain injury , and it can be associated with impaired cognitive function, headaches, fatigue, depression, anxiety and a host of other symptoms that can last indefinitely.

This is also why personal injury cases normally take a few years to resolve. Assessing the extent of certain injuries requires waiting to see how bad they get, and whether they get any better. That's why Dao's case was unconventional, and not really about the injuries. The parties didn't wait to see how Dao's recovery and treatment defined his injuries over time. They settled within weeks. This case was more about United's public relations headache, than Dao's actual headaches.

Yet, Dao didn't have as much leverage as it may have seemed he did. His injuries alone didn't strike fear in United's lawyers—airlines litigate passenger injuries all the time. Instead, United desperately needed Dao to agree to settle to stop the flurry of bad publicity.

But with each passing day, as United suffered the bad press it wanted to avoid, the amount United would pay to avoid that bad press decreased significantly. Had Dao waited a year, the one thing he had to offer—ending the bad PR—would no longer be worth anything to United. Heck, I have to imagine there were lawyers in United's camp that suggested hunkering down, waiting it out and playing hardball until few remembered the incident—as tends to happen with viral videos.

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That's why Dao's attorneys did the right thing in settling quickly. It also indicates that United probably paid well north of a million dollars. Why? Because by settling early, Dao takes a risk by giving up the opportunity to build the value of his case the traditional way: a couple years of medical records documenting the nature and extent of his injury and treatment. The settlement amount had to be a number that Dao felt comfortable accepting, even if his injuries take a turn for the worse in the future.

That's good for him, but not an indication of what other plaintiffs might get if they file cases against airlines. Dao's case is one-in-a-million. For the rest of the would-be plaintiffs out there, United will probably see you in court.