Building a road is a difficult and costly job." Why

We can't make this exactly but most of the roads are expensive like ghat roads , Road over bridges , road under bridges and depending on the topo like tunnels in hilly terrains , forests ,types of lands,suspension and bridge roads over water bodies or deep areas , more over in this decade the land aquasition became the major factor and delay of funds turns the project cost run high from the bidders. I have considered major roads and mostly the flexible pavements i.e BT roads and it comes a lesser cost in the case of CC Roads.

Explanation:

answer; curiosity;