ah, how I loved contracts but I wish I had discovered this page and your question earlier when the course was fresh in my mind but I'll give it a try "for fun"
Okay, in brief outline format of possible issues and arguments: Was there a contract formed? Statute of Frauds argument that this was a service contract that would last longer than one year. Expect Owen's wife may argue that since payment was divided for each completed house, so should it be thought of as eighty separate contracts, where each single house could plausibly be built within one year, especially since no less than 40 had to be built within the next two years. Even if Con's argument that there was no contract due to no written agreement (we simply cannot tell from the facts given), the Mrs. can argue at least for reliance damages or even expectacy damages under the doctrine of promissory estoppel, although as an advocate you must be careful. Depending on what judge you argue in front of, some just may have a record of not being fond of extending Restatement section 90 too far. However, it seems that promissory estoppel has become quite loosely used. The history of the doctrine is quite interesting (Cardozo tried to extend it from Allegheny College to Wood v Lucy in a sneaky way; and then we have Baird and Drennan construction cases. Exact same facts, different judges. Learned Hand, in disagreement with Traynor, extended the doctrine that would become irreversible from then on ---sorry for the digression). Depending if your judge is more persuaded by the Fuller and Purdue school of influence, primissory doctrine may only award reliance damages. Depends on what seems like "justice."
Also at issue is the matter of personal statisfaction- a condition that probably can not be assigned to Owen's wife since it is a very presonal matter. Con can argue that he only agreed to the part of the contract for the installation of music systems based on his own assessment that he was confident he would be able to meet Owen's tastes. Con can argue he doesn't know what the Mrs. likes. However, any argument Con makes to the sound of unilateral mistake about the availabiltiy of Fidelitone sound systems shouldn't excuse his promise since that is a risk he should have foreseen. Likewise regarding his later determination that he would lose money. Also a losing argument. Too bad, so sad- he promised and expecially as a contrator, he should know what he is committing himself to.
We are not given any numbers as to how much more Con had calculated the total project would cost him over his original contract amount. Whatever it would cost Mrs. Owen to find a reasonable market contract price to finish the project would be her expectancy interests. Expectancy damages would include any incidental costs such as phone calls and expenses searching for another contractor. Consequential costs, such as any costs to delaying the projects since it seems time was of some essence given the condition that no less than 40 houses had to be built within two years.
I'd be stoked to hear comments from anyone else. Although I'm through w/ that course, I did enjoy it thoroughly when I took it. I'd love to hear any corrections/additions; and of course, I make no guarantees as to the accuracy of the information from the recesses and cobwebs of my mind! I love law school! (yes, I have got to be a little f**ing crazy! but I do love it!