However, if you sell a vulnerability to a group that will explicitly use it for malicious purposes and this becomes very well known, you'll obviously become a polarizing figure and many doors will close on you. Not all, of course. Just a lot of high value ones.
This is not to make a moral judgment - it's just a reality that a lot of organizations won't want to be associated with you if you're labeled as a blackhat. Of course, if you do that you'll find plenty of other high value doors suddenly open up.
I don't have any good citation for the going rate for a high value vulnerability on the black market, but if you look I'm sure you'll see it can easily enter the mid six figure range.
As for "good vs evil" - I never used those words. Morality is a word I used because it provides a useful context against which to judge legitimacy. You can fairly say it is unethical to sell vulnerabilities for the explicit purpose of exploitation. I don't particularly care to color it this way; I disagree with such actions but I still respect my fellow colleagues who do it.
Also, as someone who makes their living selling exploits I rather disagree on your claim that selling vulnerabilities is something that would have you labeled as a "pariah". I don't think I've ever seen that happen.