Specifically, data is only worth as much as the buyer is able to exploit it to make money. Meta and Google have figured out how to immensely profit off of personal data - but that's because they own the largest ad networks on the planet.
Few other players can leverage personal data to this financial extent. More importantly, the players that can leverage personal data for immense profit also collect their own data, and so externally-sourced data is only of marginal utility.
And you see this in the discourse around this issue. We theorize for example that some grocery chain would "pay a lot" for personal data. But to what end? So they can offer just-in-time enticements to go to the store?
A lot of these supposed "applications" of personal data seem pretty flimsy, and even where they are genuinely useful, their monetary worth is marginal.
Data is worth something, but it isn't worth nearly as much as widely believed.
https://en.wikipedia.org/wiki/Exxon_Valdez_oil_spill
It's easy to say that data is immensely valuable, but mostly it isn't. How personalized are the ads you see on the web, really? What's the ratio of times you clicked on an ad accidentally or got tricked into clicking an ad (ever had the layout change on Anandtech just before you tried to click on a link?)
I used to work for a company that helped other companies decide where to place stores. Circa 2007 we were thinking about it from the viewpoint of trips and I'd developed a touchscreen kiosk that would get visitors to a Dairy Queen to tell us where they came from and where they were going. We believed that people didn't just go to a fast food restaurant that was convenient to their home but that they were driving from point A to point B and happen to stop at a restaurant along the way so a "good location" had a kind of centrality where it was on many such paths.
(The project was ill fated. The kiosk we selected was rather expensive, particularly for a project we'd sold to one franchisee. Our partner dumped us because he thought he could get cheaper kiosks, we brought in our lawyers, as ahead of its time as it was, we never got put the kiosk app in front of customers.)
On one level it's a good idea, but what is the data really worth? Chains that work hard at picking good locations find their competitors follow them and set up shop across the street. The value of the data is based on the amount of lift you can get using it relative to the alternatives. People often wind up choosing locations for other reasons such as Duane Reade who were geniuses at finding sites they could afford in the NYC real estate market.
Who is going to pay anything, let alone millions, for Uber trip data?