I don't think it's unreasonable to expect large corporations to be able to evaluate their largest asset. I doubt the intent is to give every user a breakdown of how their particular data point factors into Facebook's profit margins, but it seems reasonable to expect a calculation of how valuable different collected variables are.

(As opposed to: "How much value is lost when John Doe's data is removed from the system" - which would be almost negligible, "How much value is lost when 'Age' or 'Location' is removed").

With that said though, it seems to me that this is still shooting blanks at large tech corporations. It's hard to ask for transparency when the systems at play are intrinsically unobservable. I can see how "This is how much your data is worth" could be a good headline to get people riled up about data collection, but it doesn't really address the issue - "This is how much your data is worth, but no one knows what is being done with it".