I think you'll find, on a statistical basis, that graphic arts professionals are going to be a much smaller percentage of iPad Pro (on not-Pro) professional users. There was a powerful economic argument for graphic arts professionals moving to Mac. The previous technology for typesetting/layout was far, far more expensive, so purchasing even "expensive" Macs was a no-brainer.
A bit later, when digital audio and video/film production became practical, the move from early digital systems running on minicomputers with hatbox HD arrays and custom-built hardware user interfaces to Mac/PC was another financial no-brainer.
At this point, those transitions are ancient history. The cost savings from those professions moving from Mac/PC to iPad is not nearly as great, so other considerations take priority - adapting workflows, display size, hardware capabilities, software availability... the typical "iPad can't replace my Mac" arguments. Trust me, if there were really big bucks to be saved, those folks would be far more adaptable.
The real growth in professional use in many fields comes from mobility, which doesn't affect graphic arts pros nearly as much as it affects other professions. For teachers, I suppose, moving easily around a classroom or from classroom to classroom is a big deal, and stylus input is also likely a significant advantage. In other highly-mobile fields that had yet to fully migrate from paper to computer (especially healthcare), it makes much more sense to carry an iPad from room to room than continually logging in and out of desk-bound PCs or carrying a laptop.
The economic argument in these professions is that iPads are cheap enough that one-per-worker is economically practical, whereas the economics of PCs still argue for shared use (especially when you compare the costs of IT administration of PCs to iPads), and the form factor is close enough to a clipboard that it's a natural adaptation.
So, if it's going to be one-worker-one-device, then those professions with the most workers are likely to dominate the usage statistics.
And if we isolate the discussion to iPad Pro... the price spread between "regular" and Pro is not that great - it'll more likely be a measure of the worker's salary/corporate status than of actual technical requirements.