Not an expert, but... "Net gain" seems to be the "give us enough $Billions and years and we'll find it" holy grail of fusion power. Vs. a $4 Casio calculator I can buy on Amazon today includes a zero-maintenance solar cell that is good for "net gain, plus useful work". Large-scale solar and wind power are already real-world at commercial scale, with costs per MW-h that pretty much beat every alternative. ( https://en.wikipedia.org/wiki/Cost_of_electricity_by_source ) Old-type nuclear (fission) energy has a horrible "what was promised, vs. what was delivered" record.

Maybe your equations and power laws are right, and a "big enough" tokamak would be a competitive source of power. But then there are the details, like "big enough will cost $25 Trillion". Followed by delays, cost overruns, etc.

I'm thinking that a rational, non-expert taxpayer would say, "This fusion thing is a hundred times worse than NASA's Senate Launch System. Stop wasting my money on it NOW, and let gullible investors waste theirs instead."