Greenhouse production is more expensive than producing the same crop in the field, but it is difficult to generalize about how much more expensive. In estimating construction costs of a new greenhouse range, different factors may be included: greenhouse frame and cover; environmental control system; headhouses and plant growing systems. In 1993 [4], a modern greenhouse, exclusive of land was estimated at $US90-100 m-2 when the hydroponic plant growing system was included. Costs for some glasshouse ranges are as high as $140 US m-2. For just the greenhouse structure and equipment , 1998 estimates for California [5] were $52 m-2. This included frame, construction labor, heaters, fans cooling, irrigation, pump and well, electrical, and tools. Another cost is labor. Greenhouse vegetable production is very labor-intensive, requiring 7-12 workers per ha [6] unless transplants are purchased, or packing is done off-site. At least some employees must be skilled in working with computers, irrigation equipment, fertilizer injectors, plant culture, and IPM. In Canada, because of the rapid growth of the industry, lack of labor is limiting greenhouse expansion [7]. Although production is higher than in the field (see below), for greenhouse production to be profitable, a price premium must also be available because operating costs are high. An average yearly operating cost of $50 m-2 was estimated for greenhouse tomato production in California [8], including labor. Total estimated cost to produce 1 kg of tomato fruit was $1.70. This means that the quality must be consistently high and greenhouse product must be clearly differentiated from field-grown tomatoes.