Selling user behavior data to google in exchange for free analytic is exactly one of those markets which GDPR want to turn from being invisible for the persons whose behavior data get sold to visible.
If a hospital would in secret sell my medical records to drug companies in order to get free medical supplies I would object on several grounds. First because they are doing it without telling me. Second because its not their data to sell. Third because it create an unfair market where drug companies who are more ethical get out competed.
This is exactly the spirit of the GDPR. You know your data won't turn up in some completely unrelated place because of a previous business transaction.
If a hospital would in secret sell my medical records to drug companies in order to get free medical supplies I would object on several grounds. First because they are doing it without telling me. Second because its not their data to sell. Third because it create an unfair market where drug companies who are more ethical get out competed.