This doesn't seem very efficient to me.
I'm speaking as someone who has had a few hundred foot trenches dug in my yard for running cable. Extrapolating it to 0.5 miles would come out to a lot more than $30K.
e.g. I used to pay ~$2k for a contractor to come to re-gravel my driveway. Now I own my own excavator and loader and dump trailer it costs me about $200 (plus my time plus equipment depreciation).
So that means I paid for labor. But presumably some part of that $30K will be going to labor as well.
Another possibility is that when you get to the scale of 0.5 miles, you start using different tactics or machines than the small little backhoe loader that the guy used in our yard. So, more capital required but overall more efficient.
Anyway, I don't mean to try and offer an accurate accounting of all of this. I mostly just meant to provide a counter-expectation.
ATT recently did fiber by my house with some kind of machine. It did some kind of U shaped trench, where it drilled down (not sure how deep), then over about 200 feet, and back up. So you only see a hole every 200 or so feet, vs a solid trench. Let them go under driveways and all of that.
A team of 4 guys was able to do my entire neighborhood in a day. Still waiting for ATT to actually wire up the fiber, until them I am stuck with comcast cable (which is fine ,except the data cap doesn't scale with speed, so the faster connections cap cap you out in like 15 minutes).