One of the contributing factors that fuels the fallacy of sunk costs is the way business is run.  Everyone is so concerned in quarterly profit and stock prices that change hourly that they lose sight of long-term goals.  Sometimes when a project is started, the scope is simple but it creeps into something much larger and exceeds the capability of the original design.  Starting over from scratch at that point should not be discounted because the ideas generated in the first plan sprouted new ones.  That's the definition of research and development.