A jury verdict in a civil case can be overturned by the trial judge in a post-trial motion, or on appeal, if no reasonable jury could have reached the verdict based upon the facts before it. But, unless and until someone bring a post-trial motion and/or takes an appeal to its conclusion, the jury verdict stands.
But, there are many theories upon which a reasonable jury could reach a different result.
For example, in the first case, the jury could find that the seller failed to mitigate his damages by retaking the wreckage of the car and reselling it for scrap, and could have found that the value of the wrecked car was $5,000.
Also, the examples state that "At trial, Alice does not dispute the basic facts about the contract or what happened.", but in the U.S. civil litigation context it is almost impossible for cases like that to go to trial. If there is really no dispute of fact, the case will be resolved in motion practice (there are several steps of a lawsuit where this could happen), and the case would never go to a jury in the first place. No reasonable lawyer would miss an opportunity to do so in a case that was that clear.
Cases generally only go to trial when there is a genuine dispute regarding a material fact in a case.
For what it is worth, it is also the case that only about one in 10,000 civil cases with $10,000 or less in dispute are tried by jury anyway. Almost all such cases are resolved in bench trials in which a judge must justify his verdict in either an oral opinion delivered from the bench or a written opinion usually prepared after the trial and then served on both parties.