In a breach of contract case, the jury is typically asked to find both whether there was a breach, and the measure of damages. Juries are fickle. They may find a breach, but feel bad for the person (take Mowzer's example of car wreck), and as a result, they give the value of the car vs sale price. If there is a substantial difference between the two, maybe they feel she was taken advantage of.  

In any breach of contract case, the issue of damages should be calculated by the jury based on a variety of factors. A jury can do with that whatever they want, and come up with something they think is fair. If it appears clear that their determination fell well outside the facts applied to the law, then opposing counsel can ask the judge to find there to be a "judgement notwithstanding verdict" or an NOV.

This is the reversal of a jury's verdict by the trial judge when the judge believes there was no factual basis for the verdict or it was contrary to law. The judge will then enter a different verdict as "a matter of law." Essentially the judge should have required a "directed verdict" (Usually requested by counsel outside of the jury's earshot and then an instruction is given to the jury to return with a particular verdict since the facts allowed no other conclusion), and when the jury "went wrong," the judge uses the power to reverse the verdict instead of approving it, to prevent injustice. This process is commonly called "judgment N.O.V." or simply "N.O.V.," for Latin non obstante verdict. This needs to be requested at the time of the verdict (some jurisdictions give you 1-3 days) or the right to ask for this relief is lost. In a case like you originally (I didn't really read the second one) described, where they gave at least the value he was out (as opposed to what he stood to make), a judge would never overturn.

I have seen this happen once. I have seen a judge increase a verdict one time in a case with a very unlikable plaintiff and a very sympathetic defendant. He did not give the Plaintiff what he asked for, but gave him his actual losses (not contractual gains), when the jury gave him only $1. A judge very rarely overturns the findings of a jury, no matter how whacky they may appear. 

I haven't addressed you scenarios directly for the most part, as there are so many facts that go into a jury trial that could never be represented in this format to the extent that would be necessary to opine as to why the jury did what they did. However, this answer is relevant to all jury trials.