Where can I find the commission structure?

Common Questions, Adobe Stock gives an idea. You get 33% of whatever they pay on Adobe Stock for photography. What they pay per image will depend on which plan buyers sign up for as listed at Adobe Stock.

I have to admit that the commission structure for Adobe Stock is one of the most opaque out there and, bizarrely, there's a restriction on who can contribute to the "Premium Collection" which is a sort of invite-only, elitist group who are the only ones who will get to taste the joys of selling for so-called ELs i.e. Extended and Enhanced Licenses.

Why that is, I'm not sure. I think it should be up to the buyer to decide if a particular image is premium for their purposes or not and, on the flip side, just because I may be a "premium" photographer, it doesn't mean I can't upload something that no one in their right mind would pay an EL for.