Earlier quoted context omitted.
300 MJ is about 83 KWh. In the UK is 1 KWh is £0.34 So, this costs £28 in electricity to run this experiment. The experiment is a momentary thing. Clearly there is now some work to, but now this is becoming an engineering problem of how to extend, sustain, and scale this process.
To have a hope of supplying grid power, they need to scale up the energy gain by four orders of magnitude and reactor run time by 12 orders of magnitude. Those are just two of the engineering problems. It'll be a while, and I doubt it will ever compete with solar, wind, and storage.
I'm guessing in a decade we'll have a viable early stage industrial process, and in 2 decades we have commissioned fusion reactors.
If we don't kill the planet with nuclear war or the climate crisis.