I believe FB makes something like $6.50 per user. Obviously Google makes money from users too, and given overlap it seems likely that one user is worth quite a bit annually. Average that out over lifetime value, and we’re talking thousands of dollars.
Imagine if the likes of Equifax treated silos of data as a liability instead of an asset to be milked. Properly valued, a breach of hundreds of millions of people’s data would end a business, even as large as Equifax.