The 80/20 rule says that 80% value come from 20% effort. What if we apply the 80/20 rule to the first 80%?

So 80% of 80% of value come from 20% of 20% of effort. Or 64% of the value come from 4% of the effort. Apply it again and you’ll get ~51% value from ~1% effort. Which is ballpark close to “Dimidium facti, qui coepit, habet” — Well begun is half done.