More dribble, little understanding and a continued insistence that you know it all.
The facts seem pretty clear here, and the fact is that it cost $3k for a random individual to hire a contractor, who in turn got all the necessary permits and permissions and ran the line. Therefore in the absolute worst case, it would have cost Comcast... $3k to run the line.
Said random individual hired a fly-by night contractor to install said line for $3K has very little bearing on what it would cost Comcast. You have no idea if the contractor followed any of the requirements or received any of the required permits or performed the required studies or even installed it properly (such as the pull weight limits for the type of cable installed). I would in fact wager against it having been done properly because the guy probably hired the contractor that gave him the cheapest price without any regard to following the rules.
Of course the beauty of doing what he did is that he now owns the entire thing. That contractor nicked a water line that's now leaking and will end up causing frost heave that ends up destroying the roadway, it's all on the homeowner. Or the water line nick floods his neighbor's basement, guess who pays to replace the neighbors antique furniture that's now ruined. He improperly trenched the roadway and replaced the pavement with inadequate drainage and improper material which causes the roadway to fail, it's all on the homeowner. There are a million things the contractor could have done wrong, all of which that could have catastrophic consequences. The first and foremost is that if that was installed without a right-of-way permit the local jurisdiction is probably going to make him remove that line in the future, or they will remove it and charge him for the removal.
Or even the simple problem of his internet connection stops working, Comcast will deny it's on their end and will suggest he replace that line he just installed and Comcast will likely refuse to do any troubleshooting because it's not their line and not their problem. Or some other company installs a Utility in the area and cuts his line because it's not properly marked, identified or in the one call system, all the liability is on the homeowner.
That homeowner took on some big liability by installing something into the public right-of-way. I hope it doesn't come back to bite him in the ass and end up bankrupting him and ruining his life.