My favorite bit of this argument is the presumption of honesty, accuracy, or transparency on the part of developers. Someone in the estimation process is always protecting themselves, packing on a little margin, or fudging the numbers. It's nothing to get upset about, it's just normal human behavior, happens in all industries.
For this reason alone, I always kick estimates back down and amazingly they almost always come back better-optimized – usually because some trusted graybeard engineer, who has been on both 'sides' of the business, steps in and cleans it up based on his experience.
For this reason alone, I always kick estimates back down and amazingly they almost always come back better-optimized – usually because some trusted graybeard engineer, who has been on both 'sides' of the business, steps in and cleans it up based on his experience.