Perhaps as often as contracts are made, they are breached. When breaches occur, it falls to the innocent party to quantify and make a claim for their losses informally or through the courts (if they choose to do so). An award of compensation under contract law is premised upon the goal of restoring the plaintiff to the position they would have been in had the contract been performed correctly. But what are the remedial consequences if a plaintiff benefits, rather than loses, as a result of the breach? What if the benefits arise without any efforts from the plaintiff?
Giancaspro, Mark, Quantifying Damages in Cases of Advantageous Breach: The Curious Case of McDonald’s Milkshakes (October 25, 2018). Stetson Law Review, volume 48, 69-104.