Purchase and transaction histories provide very rich data profiles and are a big business. There are also several companies that match up this "offline" data with online profiles so you can be targeted online.

PII is not available, it is anonymized. There are laws around this. Purchase data itself is usually grouped into major purchase types, not amounts or actual goods purchased.

For that detail, it would be the CRM/ERP systems of the manufacturer that has that information tied to a serial number and this is why they ask you to register your product when you buy it. Some manufacturers might work with data providers to exchange this data (serial numbers in exchange for purchase histories) but it's rarely done at scale because of cost, complexity, legal/security risk and lack of options to benefit from it.