Hills? Rocks? Trees? Wire mesh? Site conditions (ie. drive to fence, carry everything 500 ft, machine dig, hand dig) this is just like everything else we do hardscaping wise, price it by how long it will take you, and add your materials. We get anywhere from from $7-$18 a linear foot for split rail depending on answers to the above questions.
GILLA thanks for the plug. Drafto is correct wih his suggestions depending on where you live Know what the competion is getting try and stay competative, diging is the most imortant factor on the labor. Here in New England most of the diging sucks. I would probably get around 12.00 per ft. for a job that size.