Energy costs don't really matter much in sustainable abundance. There's not much marginal cost, and without fluctuations or scarcity we'll just contently pay the financing charges.
The Fusion plant with have a construction cost, and operating life, maintenance schedules, and operational costs, all of which factor into LCOE.
Then there is the question of scale and any transmission upgrades.
But mostly it is a solution for 2040-2060 at best, not something relevant to between now and 2030.
People underestimate what can be done with solar and batteries, batteries can store solar for transmission 24x7, making optimal use of transmission assets.
To cope with Solar seasonal variation in the Australian state of Victoria they would need a total of 9X, Simply building X in Victoria and 2X in Queensland does the same job, (before transmission losses). That is because winter solar generation in Queensland is way better than Victoria.
So it is similar to solid state batteries, the funky new technology will be great when it arrives, in the meantime there are many opportunities to solve the problem with existing technologies or improved versions of existing technologies.
Even if Fusion represented some threat to Tesla energy by say 2050, there is a lot of opportunity for Tesla energy to make money between now and 2050 and every chance Tesla will be further diversified by 2050.
For solar it would be great to take energy from more of the spectrum, and have some ability to generate electricity on cloudy days. That isn't science fiction, the proprieties of the light spectrum are well known, currently we only tap a small portion of it. Would this improved solar arrive before Fusion? IMO Yes.