"what becomes cheaper is the individual machine and its component parts, but a system of machinery develops, the tool is not simply replaced by a single machine, but by a whole system, and the tools which perhaps played the major part previously...are now assembled in thousands. Each individual machine confronting the worker is itself a colossal assembly of instruments which he formerly used singly...But in addition, the machine contains elements which the old instrument did not have. Despite the cheapening of the individual elements, the price of the whole aggregate increases enormously and the [increase in] productivity consists in the continuous expansion of machinery. (Marx, Theories of Surplus Value, Part III, p.366)