A contract between DJ Billy and the Barrow couple, specified that DJ Tony would play music at the Barrow's wedding in Toronto in July 2019. Three months before the wedding, DJ Billy informed the couple that he would no longer be able to play at their wedding because he had a more lucrative contract requiring him to perform at a music festival the same weekend (meaning the profit from the music festival was substantially more than that from the wedding).

DJ Billy is now appealing a lower court ruling that allows the Barrows to recover expenses related to the wedding, before and after the contract between the two parties was terminated. In essence, DJ Billy is challenging the scope of the expenses. What are the economic challenges for judges ruling in this case and cases of a similar nature? Please explain, using contracts, efficiency and social welfare as the basis for your position.