Paid user base or free user base? Because free user base on a very expensive product is next to meaningless.

It's meaningful because it shows that people like the product a lot, and for a lot of different reasons. There are only few products that can reach such market penetration, not to mention in only three years. As the quality of AI increases, people will quickly realise that they are willing to pay for it as much as they pay for electricity. And the same goes for businesses.