The problem is Amazon, Ebay etc don't want this at all, they wont give you access to their data if you try to do anything meaningful with it for yourself as a end-user because they dont want you finding something cheaper somewhere else, they want you to buy from them, or whatever profits them most otherwise why sell "ads" for products within their stores?
Indeed. It would be interesting instead of some of the Lina Khan style "cleave a company apart" trust busting we instead had a push for government action to enforce this state of affairs, given the nature of the private incentives.
This would also be more transparently a benefit to consumers, as I recall one of the hurdles in the present state of anti monopoly law is present monopolies (like notably Amazon) have rather obviously reduced costs/made life easier for consumers.
This tension between these companies and consumers becomes more obvious as companies resist these moves while more and more consumers adopt LLM intermediaries.