From making it to selling it
The slicer finished its estimate. Your work has barely started.
The customer sends a file. The slicer reports a few dollars of filament, and a quick price feels easy to send. But you still have to check the model, prepare the plate, remove the supports, and finish the part. Those steps need your time even when the printer runs unattended.
A second attempt consumes more material and time before you have anything to deliver. A useful estimate joins the slicer's figures to the rest of the job, using your actual process rather than asking filament alone to represent your shop.