Being frugal was not his problem.
Powering down and unplugging the machine for a few minutes before opening it would have spared the man's life.
Not taking simple and fairly obvious safety precautions was. He may have done this many times before and gotten away with it as most people do when they take foolish chances.
Five minutes for a reboot would have saved his life.
It sounds like he ran the computer without a cover habitually, in order to prevent overheating of the chip. In a modern ducted cooling machine, of course, heat control is better with the cover on than with the cover off. But I have no idea what this guy was running.
There are bits in there that can hurt you, presumably. I am looking at the guts of my computer right now, and am seriously considering replacing the cover. First I will have to find it, since it has not been on in a couple of years.
But I don’t go sticking my sweaty leg in there, or anything...