Not an engineer in this field, so I may have misread/misunderstood, but I read that 2.5MJ out for 2.1MJ of laser energy in, NOT the total energy needed to make the whole thing work.. So, in a layman’s world, it is not a net gain of power, only a small subset of the system yielding more power than it took in.

Happy to be proven wrong and told that it is more of a breakthrough than I think it is..