“People are willing to pay for it” is not even relevant to the question of whether it’s rent-seeking. Rent-seeking has to do with capturing unearned wealth, i.e. taking someone else’s work and profiting from it.
There is some portion of OAI’s (et al.) value that they themselves produce. There is another portion that is totally derivative of the data — other people’s work — they have trained on for free. A simple thought experiment can tell you to what degree OAI et al are “rent-seekers.”
Imagine a world where they had to enter into mutual agreements in order to train on that data. How much would the AI companies be worth? Not quite zero, but fairly close (Andreessen pretty much stated this IIRC). How much would the data producers be worth? The exact same amount or more.