Always find it very annoying how ridiculously expensive various items are for railroads and I'm sure this goes into other industries as well. A few IR sensors some custom printed circuit boards and a computer that most likely does not need to be any more powerful than your most basic entry level smartphone for a hot box detector cost as much money as a supercar with many thousands of precision made parts. You're basically talking something a bunch of vocational High School kids could design and build for under five grand. Furthermore why are we even still relying on HotBox detectors when you could just mount a rubber hose connected to train air over the adapter plate of a truck so if it overheats the heat generated will melt the hose dumping the train air?