There are different qualities of email databases. "Known real email by Youtube account holders" would be a high value database. Definitely not free.
This type of vulnerability is extremely valuable for private investigators, too. "Who uploaded this video which my client is extremely interested in?"
Would exploiting this vulnerability violate the Computer Fraud and Abuse Act? If so, would a private investigator really want to do that?
https://www.stltoday.com/news/local/government-politics/pars...
That database only exists in theory, based on extrapolation of this vulnerability to billions of individual exploits, and I think we can all agree that Google would detect this activity and shut it down.
Hence, that database might fetch a decent price if it existed, but it doesn't.