It is much cheaper to do it correctly the first time than to redo it later on. The sooner a problem is identified and fixed, the cheaper it is to do so.
“The general who wins a battle makes many calculations in his temple before the battle is fought. The general who loses a battle makes but few calculations beforehand. Thus do many calculations lead to victory, and few calculations to defeat: how much more no calculation at all! It is by attention to this point that I can foresee who is likely to win or lose.”
“Plans are worthless, planning is invaluable.”- Sir Winston Churchill
For this to work, everyone involved has to listen, everyone has to be open, everyone has to be responsive. Or we could keep flailing away with the fucked up attitude that “it has to be this way” because the sacred project plan says it’s this way. Because that really is a lot of fun, isn’t it?