iPad Pros are not meant for the average tablet user. Non-Pro iPads are already arguably vastly superior to the Android competition in many ways, at affordable price points. And for those who want something more, they can get the iPad Airs. The iPad Pros are at the high end.
Sure every product tier has its price limits, but it's not as if Apple is trying to compete with $500 tablets with the iPad Pro line.
I think Apple will price the OLED iPad Pros to a level Apple thinks the market will bear, and won't just base it off the cost of the components with a fixed margin markup. Apple will sometimes increase or decrease margins accordingly. If Apple thinks it makes the most sense to keep the price fixed, it will do so, even if components cost more. I don't think they will do that, but another option as mentioned in this thread is to increase storage while increasing pricing at the same time. Or maybe they will keep the storage the same and increase pricing, but if they do that, I don't think they'd increase it more than US$50-$100.