Traditionally, and depending on the commodity, marginal cost can on rare occasions rise, sometimes stays flat, and often falls. With this more modern phenomena

Traditionally, and depending on the commodity, marginal cost can on rare occasions rise, sometimes stays flat, and often falls. With this more modern phenomena for digital products, almost all the costs go into creating the very first product, and then with the production of the copy and subsequent copies the cost of subsequent products falls to near-nothing or nothing. It could be called marginal cost if so desired, but this phenomenon is new in terms of its weight within the economy.