That 50m+ figure is surely iPads in general, rather than iPads Pro? iPad Pro is specifically marketed to media production professionals as a viable replacement for a laptop, but media production professionals (like the aforementioned tech youtuber) again and again complain that it isn't good enough. It's certainly good for some professional tasks, like drawing, but it seems lacking for things like video editing.
Even if they made every single one of them buy a new ipad every single year that would still be single digit change of revenue for apple