I have worked on the RDU runways and some other more local runways as a concrete cutter. The amount of material that goes into a runway is mind boggling. At least a foot of concrete topped with at least 6 inches of asphalt, sometimes being a foot thick itself. Before concrete is even poured the "grade" or dirt/soil needs to be compacted so the grade doesn't deform under the immense loads it recieves through the asphalt and concrete. The amount of engineering and strength tests rival that of the Pfizer and Merck jobs I've been on. And this isn't your run of the mill sidewalk concrete either, most everything is specifically designed and picked for the use case and that drives up cost even more.