Set up material for planning purposes - run size differences

Looking for some advice about handle a certain dynamic that has presented itself from one of our plants.

How would you build in a static qty of necessary set up material, that is not dependant upon the size of the WO?

This circumstance comes to us from a factory that prints artwork on plastic film.

The situation is that regardless of how large the total production order is (10,000 ft, 50,000 ft, 100, 000 ft, etc) there is a necessary qty of material that you have to push through the printing machine at the beginning of the job just to get it rolling and producing good product. They call this "start up scrap".