<p>The number moved because the model moved. BidLight keeps one live record of the project inside Revit and Navisworks, so when someone edits geometry or metadata, the cost tied to that same model updates with it. Last month&#39;s estimate was a snapshot. This month&#39;s is the current state of the design.</p> <p>Where the $340K usually comes from:</p> <ol><li>Scope added since the last export. New elements carry their own labor, equipment, material, and time.</li><li>Quantities changed on existing elements. A duct route gets longer, a wall assembly gets thicker, counts go up.</li><li>Classification changed. Two AI models read geometry and metadata and sort line items at 86% accuracy. A reclassified item can land in a different cost bucket than before.</li><li>Pricing refreshed. Rates pull from a roughly $30,000 database plus Craftsman, 1Build, and RSMeans, so current numbers can differ from what you sent.</li><li>Rate or productivity assumptions were edited by whoever owns the estimate.</li></ol> <p>Every export is versioned and diffed element by element, so you can show the owner exactly which changes drove the delta. That is the defensible answer, not a guess. If you had done the takeoff by hand, you would be hunting PDFs side by side. Here it is already traced back to the elements.</p>