I don't charge by the square footage for pre-wire, but was curious and looked back at the last 4 jobs.  My pricing was around $2.50-$3.00 per square foot.

These were 8-12k square foot homes with Phone, TV, Network, A/V plus low voltage wiring for Lutron keypads and shades.  Pre-wires are fairly complex with lots of concrete and steel, no basements and very little or no attic space so include lots of conduit and often span 3-6 months.