Case:

Ruling : One who reneges on a sale where no kinyan was done is considered one who "lacks trustworthiness," a distinction one should avoid. The Rama (CM 204:11) cites different opinions whether this applies even if the market price changed in the interim. The same laws applies to employment agreements. Whether def should have backed out when a free band became available depends on that machloket. The Chatam Sofer (CM 102) rules that a planned buyer may back out if he received in the interim the object as inheritance. Therefore, one can be lenient here as well.
The Shulchan Aruch (CM 333:2) says that if one orally hires a worker who could have found a job at the time and now cannot, he must pay for his lost employment. In this case, pl had another offer and was not able to find an alternative appearance with short notice and deserves reimbursement. Def was not forced to cancel pl’s appearance and willfully chose the preferred arrangement.
The Shulchan Aruch (ibid) says that the payment for cancellation is only partial- as a po’el batel. In other words, we consider how much most people are willing to reduce their income in order to not have to work during that time. The gemara (Bava Metzia 77a) says that certain workers receive full payment because when they do not work, their bodies weaken. The question is whether we can extrapolate from that case and say that pl was interested to appear and therefore nothing should be reduced from the fee of 5,000 shekels. The Minchat Tzvi (Spitz) says that we look at the particulars of each specific case and where the worker would not have wanted the vacation (e.g., our case) give the worker the full salary. In contrast, Rav Asher Weiss says that Chazal were aware that many workers prefer to work and still they did not generally distinguish between workers. Only in a case where there is a clear external reason to work do we say that they get full pay. However, it seems that all would agree that the need for publicity is sufficient reason to entitle pl full pay.
Pl is not entitled to damages due to lack of publicity, as def had not accepted on itself the obligation to publicize. Thus, claims of lost opportunities are that of gerama (indirect damages), which do not warrant payment.