It's simple math. The "total pay package" of working in a ski area is x, which include a free pass as a substantial part. When the pass cost goes down, they need to make it up so the TPP remains the same.
I once work for a small company that provides free lunch. No just a few energy bars, but catered lunch. When the company got bigger, the catered lunch got too complicated/expensive to manage. So they took the lunch away but only provide free soft drinks. They know enough to raised the pay of the employee to compensate. Same principle.
But again, the cheap passes erode the value of those perks too. The perks are not worth as much when you can get it in other ways for less.
The real problem is ski area doesn't need to pay more for instructors. There's a line of new trainees "hobby instructors" waiting outside! They're willing to get paid next to nothing. I should know. I was once one of them "hobby instructors". My take home was only enough to pay for my gas to get there and back! I resorted to bringing my own lunch so I at least break even. It took 2 season before I concluded it's not worth continuing. But in that time, I already introduced two others like me, who also quit after a couple seasons. Resorts can actually sustain with these rotating cast of hobby instructors. Guest experience? Well, you know that already.
The current Covid related shortage is temporary. I think resorts will be hesitant to raise pay too quickly.