Rich, Thank you for your question. That is a fairly small size for an office building, which puts upwards pressure on the price per square foot. While the chart would suggest a cost in the neighborhood of $160 per square foot, the small square footage could easily push you up into the $200 per square-foot range.he data for this year indicates a $15-$30 per square foot or approximately 13% increase in construction cost over last year, depending on region.