Edit: Would be nice to have a link to refer back to the discussion that led to the bet. To my knowledge, most bets do not provide such a citation.
A price competitive 10 MW generator probably meets that standard though (Islands, small towns, isolated mills, etc).
The 5th fleet is in the Gulf to protect the flow of Oil.
The USD is backed to some extent by petrodollar, and that is a geopolitical hammer the Americans like to use at least to some extent.
So what does 'profitable' mean?
If Climate Change gets really problematic quickly, then guess what, all Nuclear Plants become considerably more profitable because the government will socialize the losses in case of catastrophic failure meaning owners don't pay for massive insurance costs which are a problem for profitability today give the possibility of $100B payouts in the case of failure.
I'm wary of the commentator's cynicism. If we can make demo plants operating at some scale, close to break even in 25 years ... then that's a strong hint there's material progress, and that those plants could be breaking even another 25 years later.
It also easily justifies a number of scientists working on it now even if only pans out in 50 years. The long term surpluses are potentially ginormous, like, to the point where they existentially shape the future, much like carbon fuels triggered the industrial revolution.
(I do think it's entirely possible that fusion will be solidly profitable, especially with carbon pricing.)
General Fusion abandoned their first scheme because of at least three showstoppers (vaporization of the liquid metal wall, Richtmyer-Meshkov instability turning the implosion into jets of metal, and stochastic magnetic field lines in the spheromak causing unacceptable loss of energy via electrons to the metal). The new scheme has extremely serious engineering problems (the central pillar will be in a radiation/thermal environment orders of magnitude worse than the walls of ITER, and subject to extreme JxB forces). And they've never produced a neutron, as far as I know.
Rostoker et al. were told 20+ years ago that their p-11B concept couldn't work, for at least eight different reasons.
https://www.researchgate.net/publication/235032059_Comments_...
If I had to bet on any current private fusion effort I'd choose either Zap Energy or Helion.
The other problem is that size is also related to reliability. A fusion reactor will have many more parts than a fission reactor. It will also be much more complex, and operate at higher radiation and thermal stresses. This is particularly important because it is very difficult to repair something that is so radioactive that hands-on access is not possible.