I would too be pissed off if somebody lied about advertised weight. By 15%. It's not a matter of 20 g. Most people would probably be pissed if they bought a 20 lb bike that actually weighed 23 lbs. This isn't a question about tolerances at all.
Originally Posted by orcanova
Production costs are one of their promary considerations and manufacturers don't waste raw material because they're not paying attention.
Raw materials costs are actually pretty neglegible when compared to manfucaturing costs (die wear, material processing, etc, etc)