Comment by dale_glass

True, but we've built tokamaks and we're building ITER, which so far has an estimated price of between $45 billion and $65 billion.

Now of course that's a research reactor full of experiments and instrumentation that wouldn't be part of a normal power plant, but given current experience that I think we can expect we won't suddenly knock down the cost to $100M. It's going to be somewhere in the billions. And we have expectations of that DEMO is going to make 750MWe.

We can then plug those estimates into the calculator and basically figure out how cheap and how powerful a fusion reactor has to be for it to make economical sense.