A satellite constellation like this will actually be more efficient for long distance communication than fiber as hops will be more or less a straight line between a few sats whereas fiber on the ground often takes crazy paths due to terrain and politics.

If SpaceX can prove reusability, which is looking likely, putting up a constellation like this will become significantly cheaper. They also can just reuse first stages that their own customers already paid for (their customers pay for the flight, not the stage itself).