Yes, I agree with you, I am sure the many hours you spent huddled over a computer, cringing that mouse, the countless copy, and pastes, the countless number of deals that feel through, people do not factor those into their opportunity costs. If you are a student, yes, could be a good way to make cash, if you have time, and are willing to basically spam people. Unsolicited mail, offering goods or services, is considered spam. As you will find out, the number of highly populated last names will deplete, and you are working with less desirable inventory, and working twice as hard, for half as much. I feel development, or lead generation is a better way to go, to many auto script emails spamming end users from india, or the famous alex, or what not, they are not as receptive to emails from domainers as they have been.
Like for instance, I see you are selling a domain mentioned Abbotfordvets.com or something, now tell me you haven't already sent emails to the end users, and with no success, are selling the domain on dnforum. It is a very specific domain, and matches it's end users well, but as easy as the name seems to sell, it is never an easy task.