The actual work is cheap, but laying down the fiber is the most expensive because the incumbents purposefully make the process long and requires jumping through a lot of hoops.

Even if laying fiber would cost $0, it is still not a good idea to do it. The way things are currently if there are 10 competitors one would have 10 have then fiber cables go to their house, or every time one would change an ISP you will have to wait for new wire to be laid, potentially coordinating with neighbors, if it would have to go through their property.

Most people will only need a single fiber.