I see the number 150 an awful lot of times in this list.

I wonder, what is the rationale behind 150 being considered the minimum required to be able to get "extensive user data"?

(Let's forget the max nr. 250 for a second, since we can assume that an upper limit is only restricted by the amount of budget available, and would at some level be of no additional use.
It's the 150 that is more important, since it's being talked about like some sort of "entry level".)

Care to elaborate?