That's my issue. You're instating a hypothetical baseline, when it doesn't even make sense.
One, Goku's Spirit Bomb, like Moro's drain, affects all life on the planet. Even
micro-organisms, apparently. This would mean that logically, it should be much stronger than what it is and closer to the Moro Arc's portrayal.
Two, Against Frieza Goku took the
Namekian Solar System. So this scaling doesn't hold up. Your only example is Earth.
Three, due to what we know of the Moro Arc, there is no way to mathematically correlate a "minimum" or "resultant effect," because the
pool it drains from is cosmic. Hell, the fact
Goku was interrupted and thus
prevented him from making one capable of beating Oozaru Vegeta, proves that it's related to a plethora of variables, including how long he can drain, the
amount of life avaliable, (in fact, it's explicitly noted to be a limit so bad that Goku couldn't
possibly create a good enough Spirit Bomb with only Namek's energy, and
even draining multiple planets for an extended period WAS NOT ENOUGH, meaning there is no "BASELINE" that can be GLEANED, as it is VARIABLE), and due to fact it's literally
infinite energy, it's borderline unscaleable because a fraction of infinite energy would be...
infinite energy. (Though this would be more a Wiki issue than a Dragon Ball issue, but even THEN we see THIS IS THE CASE, because the fractions of energy that hurt SSB Vegeta and SSB Goku are 2-C, and yet STILL beneath the full planet's energy). And, again, due to these circumstances, the
logical conclusion or the argument is that, given they are siphoning from this infinite supply of raw physical power, that those various fighters are vastly stronger than they actually are.