"Hunh, ComplicatedX is expensive and 20% of the project is causing 80% of the overruns. We should just do SimpleY, we get 80% of the value for 20% of the price!

"Hunh, ComplicatedX is expensive and 20% of the project is causing 80% of the overruns. We should just do SimpleY, we get 80% of the value for 20% of the price!" ...Ten years later... "SimpleY is no longer Simple, it turns out that although we got 80% of what we wanted for 20% of the price, the last 20% of what we wanted were responsible for 80% of the overruns!"