Here, Mail Spamming and Gold Mining are related to FALSE POSITIVE cases which are expensive at cost. But Viral Outbreak is a FALSE NEGATIVE case which infects a lot of people on health and leads to expenditure of money too for checkups.
So, False Negative case (VIRAL OUTBREAK) are more crucial and dangerous when compared to FALSE POSITIVE cases.
a. If the model always predicts that the mail is spam, people would not look at it and eventually might lose important information. False Positive condition would have a high cost. (predicting the mail as spam while the mail is not spam)
b. A model saying that there exists treasure at a point and you keep on digging there but it turns out that it is a false alarm. False Positive case is very costly. (predicting there is a treasure but there is no treasure)
c. A deadly virus has started spreading and the model which is supposed to predict a viral outbreak does not detect it. The virus might spread widely and infect a lot of people. Hence, False Negative can be dangerous