Frankly I'm not sure where the scam has a greater effect: at the estimate or the implementation. Probably a little bit of each, of course, but I think intentionally deflated estimates are the worse crime because they are the ideas upon which reality is built. That is, construction and production costs can be renegotiated, clawed back, or otherwise affected by things people can actually do, while estimates are made-up, set in stone, then used to calibrate everything else down the line. This process is not a great human achievement.