One way to furnish a living room is with modular furniture. Instead of buying a standard sofa, for example, one can buy a left end, a right end, and a middle piece that can be combined to create an L-shaped sofa. Modular furniture, however, is far more expensive than standard furniture. On average, a three-piece modular sofa costs almost twice as much as a standard sofa of comparable size and quality. Each of the following, if true, helps to account for the greater cost of modular furniture EXCEPT: ['Modular sofas, on average, have a greater area of upholstered surfaces than do standard sofas.', 'Modular furniture, unlike standard furniture, is not mass-produced.', 'The consumer demand for sofas sometimes increases more quickly than the supply.', 'Because modular furniture pieces are custom ordered, they are never put on sale.']