Interestingly, there is a flashing red/yellow light there (similar to [1]) and plenty of houses/powerlines, so it shouldn't be the power costs. I imagine the price of buying and laying signal cable might be similarly expensive, however, as the nearest signaled intersection is about two miles away, if I recall correctly.

[1] https://safety.fhwa.dot.gov/intersection/other_topics/fhwasa...