I thought it would have been “American male 20-25, likes guitars, looking at article about cars” without any ID that bidders can attach to the next auction.
Google provides to anyone registered to bid on a given auction a unique ID and a lot of demographic data about the person browsing, but nothing that would directly identify them.
The advertisers, ad networks, publishers etc. participate in a kind of complicated handshaking that matches these "anonymous" IDs to entries in databases they've purchased from vendors who do sell your data, legally, due to all the various terms of service you click through in your life. These databases enable a link from the Google ID to everything that's ever been collected about you, from disparate sources, and aggregated on your email address or whatever.
This may well be against Google's terms of service for participating in RTB, but Google doesn't police it and looks the other way because they're making money. Just like Amazon is halfhearted about cracking down on fraud now that they can launder the reputational hit to third party sellers.
So there's a huge ass data marketplace that Google doesn't directly sell PII to, but enables to exist and be effective at using your PII and everything anyone knows about you.
Try to count up how many companies participate in this marketplace and then ask why it would all need to exist if the majority of ad impressions shown were anonymous and only broadly targeted. What are all those data engineers and data scientists in ad tech doing?
Think about why it would be worthwhile to buy and sell all this data in a world where Google of all orgs wasn't enabling it to be useful.
It's not casually purchasable in that manner. The industry has a certain level of gatekeeping and obfuscation in order to avoid people clearly understanding what's going on.
They absolutely do sell your data, but only if you’re big enough and have enough money, and are discrete enough. They invited me as part of a role I played at a globo mega corp famous for being discrete, rich, and sophisticated with data to buy access to highly dimensional real time local data with amazingly detailed resolution, ability to structure and query, etc. You could do stuff like see what everyone who drives an EV is doing, what coffee shops are popular right now with liberals, etc, all in real time and with deep comparative history. It was remarkable the detail accessible on everyone everywhere all at once. It was anonymized and aggregated, so I couldn’t buy your specific data, and it was masked with differential privacy techniques - but you could certainly say they sell your data. They sold it to me.
I thought it would have been “American male 20-25, likes guitars, looking at article about cars” without any ID that bidders can attach to the next auction.