Overhead power lines are infinitely expensive

...if people don't want them there and fight their construction. That's how to justify locating power cables under water, which this article says is an increasing trend. Apparently the cables can adversely affect fish spawning when they pass through spawning areas, and in polluted areas they can stir up nasty stuff that's accumulated on the bottom of the body of water they pass through. Of course that needs to be weighed against the damages of putting lines on land, which include removal of vegetation and the construction of towers. Overall it's apparently a little more expensive, but a little lighter on the environment. Maybe if all the costs are accounted for it's just the right solution!