That's a lot of money. You could make a lot of ground jumpers yourself for that much.
I'm an electrical engineer.
There's some creadance in assuring a uniform/effective ground throughout the electrical system of a car, and it's not rocket science. The high current loads that could cause a ground to creep away from ideal are the lights, the ignition, the starter motor, the fan motor, the heater motor, etc. When several of these loads share the same pathway, their contributed effect could reduce the voltage to the loads.
The approach of creating a "ground central" distribution block near the battery is a sound one. Then stout wires from there to the engine block for ingy, and sensors... to the body up near the headlights... to the cabin (dash) area for many apps... etc.
These measures might be argued, since pretty wise guys designed the car, but personal experience has taught me that they always watch their pennies. This means it's not "super over engineered". I've solved radiator rot, fender rot, flicker lights, and a host of gremlin-like dash problems just by correcting the aging affects of factory wiring when it comes to grounds.
I typically change my black battery cable out for one made of welding wire (many fine elements make better flow and maintain flexibility), and use a marine type battery post clamp. At that clamp, I make additional wires for body and engine. That takes care of it.
Gar