In contrast, the incidence proportion can be calculated as 16 â 2,100 = 7.6 cases per 1,000 population during the four-year period, or an average of 1.9 cases per 1,000 per year (7.6 divided by 4 years).
The Costs. Minimum Cost: Approximately $.50 per square foot. Maximum Cost: Approximately $2 per square foot. The size of roofs vary immensely from a standard, urban roof measuring about 800-square-feet to suburban roofs, which often range above 1,500-square-feet.aximum Cost: Approximately $2 per square foot. The size of roofs vary immensely from a standard, urban roof measuring about 800-square-feet to suburban roofs, which often range above 1,500-square-feet.
Tile Roofing Prices. On average, tile roofs cost $700 to $800 per square to install, though they can cost anywhere between $400 and $1,000 per square. Tiles come in clay or concrete but can be shaped in many different ways even to the point of looking like wood shake.