"Digging underground is expensive" isn't that justified, it always depends on the environment in which you're digging.
In city/village areas with roads, shitloads of existing cables and pipes it literally can take days to dig a trench deep enough to bury a telco cable pipe (here, 60cm below ground minimum - most electricity in the 230VAC level is also at this ground level, 20kVAC and water are deeper in most cases) due to all the cable crossings.
In rural areas you can usually just forget about cable crossings and easily do hundreds of meters a day (we call this "Bodenrakete" aka ground rocket).
(I'm working as a digger and technician in Germany for the current 100mbit/s-in-the-fucking-desert campaign)
In city/village areas with roads, shitloads of existing cables and pipes it literally can take days to dig a trench deep enough to bury a telco cable pipe (here, 60cm below ground minimum - most electricity in the 230VAC level is also at this ground level, 20kVAC and water are deeper in most cases) due to all the cable crossings.
In rural areas you can usually just forget about cable crossings and easily do hundreds of meters a day (we call this "Bodenrakete" aka ground rocket).
(I'm working as a digger and technician in Germany for the current 100mbit/s-in-the-fucking-desert campaign)