How to include cost associated with rare building cleaning?

This relates to a questioned I posed on the IEQ cleaning equipment forum in regards to where to draw the line. Fro the cleaning equipment forum I was told to include ALL equipment including vendors that make quarterly or annual visits. We have vendors that come on a quaterly basis to do wood, metal, stone repairs, thus they do not store chemicals in our building. They do use some GS products which we would like to include, but I am not sure how to put a cost on these products as they go with the vendor from building to building and are not directly purchased for the building. Please explain how I can go about measuring these costs?