¹²According to the book Philosophy in Practice (second edition) published by Fluke, the initial expense of their Josephson Array in 1992 was $85000, with another $25000 budgeted for start-up costs. The annual operating cost of the array is approximately $10000, mostly due to the cost of the liquid helium refrigerant necessary to keep the Josephson junction array at a superconducting temperature. This consumable cost does not include the salary of the personnel needed to maintain the system, either. Presumably, a metrology lab of this caliber would employ several engineers and scientists to maintain all standards in top condition and to perform continuing metrological research.