From my experience, the budget overruns that hit hardest are the ones caused by uncoordinated drawings between different trades. You think everything is good to go, then suddenly mechanical ducts clash with structural beams, and you're looking at expensive rework and delays. That's exactly why a solid constructability review early in design is critical. As https://www.fields-builds.com/blog/cutting-costs-avoiding-delays-constructability-reviews points out, catching these inter-disciplinary conflicts before breaking ground is the only way to avoid those costly change orders and keep the schedule on track.