Value

Value=Function/cost
Value is the exchange for which customer pays.

Value can also equate to quality over Cost, ie the higher the quality the lower should be the cost in the real context.It can also construed being tha higher the quality is the higher the cost of implementing it, but this is not the kind we talk about.No doubt that some times it takes higher cost to improve quality but in the long term cost like hidden, opportunity cost will be reduced perpertually.