I sit down and figure out all the material it's going to take. That includes every single connector, strap, screws, bushings, trencher rental, permits, etc.. Then I add 15% - 20% because I'll probably forget something. Figuring out how much time it's going to take is the hard part. Without being there I'd say four 8 hour days would be about right. I charge $50 per hour for residential. This would easily be a $3000 - $4000 job.