cost per yard is a mechanical usage of measurement used for construction while run length is usually used in coding.
Explanation:
While it may be used it construction the concept of a run length is usually reserved for the usage of programming where it is the total running of a program accounted for in the pricing
Cost per yard is a measurement of area covered in a construction and cost of the material that would be used to cover the same area.Here the variable would be the availability and the cost of the material being talked about.