Mediums are themselves services that a consumer decides whether to use based on marginal cost and utility.
They are services that are used to purchase products and services. Purchase decisions are made about these services in the same manner as purchase decisions about the end product, at least under the rational choice theory of economics.
They are services that are used to purchase products and services. Purchase decisions are made about these services in the same manner as purchase decisions about the end product, at least under the rational choice theory of economics.