I received an email to a friend who is a professor of horticulture and have some current overhead numbers for wholesale production planning is 23¢ per square foot. This is strictly overhead cost of production in greenhouses. Not plant, soil, or debt retirement. From past work with production planning and a number of nation wide surveys of commercial greenhouse production done, these numbers have been remarkably accurate, for planning. For a retail greenhouse the cost per square foot is 30¢, not as interesting. In 1995, the last year I helped with the national study the cost was only 21¢ for wholesale growers.
Millers Mutual, the only large insurer of wholesale greenhouses, uses this number in there calculation for various types of coverage.
Two publication to look at that are being quoted from a great deal are from the University of Arkansas plant science division, extension publications. Part 2 has the numbers you are looking for.