Well run businesses are always good reading, even if their stories are usually embellished. Starting the design of fashion accessories from a market price or organizing to allow chefs in a restaurant chain to experiment with new dishes, however, just sounds like good management, not examples of “Lean Thinking.”

I have never found much depth in the contrasting of “Margin = Price – Cost” with “Price = Cost + Margin,” maybe  because I have never worked in a cost-plus business. Commercial manufacturers usually do not have the power to set prices this way. Perhaps, the Big Three US automakers did have that power in the 1950s, and Toyota didn’t.

In Tracy Kidder’s 1985 documentary book House,  a Boston lawyer hired a local contractor named to build a house in the suburbs. The contractor rigorously calculated the costs of the materials and labor, tacked on a 10% profit, and presented a bid with no wiggle room. It was not intended for negotiation, but the lawyer just had to wrangle some concession out of the contractor.  The culture clash between the two makes great reading, but also throws light on how “cost-plus” works in practice.

The equation “Margin = Price – Cost” is based on the assumption that Price and Cost are characteristics of the same nature, both attached to each unit of product. It is true of Price: whenever a unit is sold — in whatever form and however it is financed — it has a unit price, and it is not ambiguous.

Unit cost, on the other hand, is the result of allocations among products and over time done in a myriad different ways, with different results. By shifting overhead around, managers make the products they like appear cheap, and the ones they want to kill appear expensive. Once the “expensive” products are terminated, the same overhead is spread among fewer survivors, thus making new ones unprofitable, and the death spiral ends only with closure of the factory.

Instead of the simplistic  “Margin = Price – Cost” for each unit, a sound economic analysis of manufacturing considers the flows of revenues and expenses associated with making a product in given volumes over its life cycle, and sometimes a product family rather than an individual products with, for example, some products given away as free samples to promote the sale of other products.