It was noticeable in the airborne weapons industry that, since most only did one thing, costs didn't get badly out of hand. If I remember correctly WE177 was completed more or less on time of around 5 years and within 10% of the original estimate.
As Dengue_Dude says it's the " Please design and build an air superiority fighter with 30mm cannon and A/A missile capability", 3 years later they say "Oh we now need it to be able to drop bombs and do ground attack" that causes a lot of the problems.