In the real world, vulnerabilities are sold to blackhat groups who want to make a profit by attacking as many websites as possible. Generally, these websites will have valuable credit card or other information that can be stolen from a compromised server.
Compromised user accounts (not even the server! just users!) on a single website do not constitute a valuable target.
The idea that TMZ would pay a significant amount of money for this is a Hollywood plot, nothing more. Vulnerabilities are not valued highly just because you can come up with a contrived scenario in which it would be valuable to someone for some reason.
This is a market, and like any other market there are buyers and sellers who dictate supply and demand.