The power output of the kind of nuclear fusion reactor we would likely end up using is going to be similar to that of a fission reactor. This reaches between 1 to 1.7 gigawatts. The cost per kilowatt of electricity cannot be known at this point. However, the team at ITER claims this would require operational experience which would only be available once a team has operated it for quite some time. Just like with all new technology, the cost will be expensive at first and then gradually become less expensive. For nuclear fusion tech, it is quite likely that many governments will use it to power cities and major facilities. Therefore, we can potentially expect governments to use their own fusion reactor tech. Yet for those that need a privatized version of this energy, the cost will most certainly be high at first.