You are having a fence built and there are pine tree roots where the posts will go and the fence builder says it will cost more Is that true?

It's very true. I run a fence business in Dallas and Houston that has been around for 25 yrs. and we always add at least $15 a hole that has roots in it. They will tear up your digging machine and take, sometimes, up to 4 times as much work to dig the normal hole free of debris.