The rock in an open trench is the only thing that explains an Austin bid
Somebody comparing three quotes has no reference for what digging costs here, and a video gives them one in seconds.
Shallow limestone and karst run under a lot of this metro, with caliche in the mix, and a line that gets dug in an afternoon somewhere else gets cut here. Rock excavation is the difference between two numbers a homeowner cannot otherwise tell apart.
Show the machine, the spoil pile and the wall of the trench. A viewer does not need the geology explained, only the picture, and the picture does the arguing.
Say what changes the price without quoting one. Depth, access to the yard, whether the line runs under a driveway, whether the rock starts near the surface. A homeowner who understands the variables stops treating your bid as a random number.
Show the odd ones too. A void where the bit dropped through soft limestone, or a seam of caliche that turned a short cut into a morning, is what makes an ordinary trench believable to somebody in Circle C who has only ever dug a fence post.