Earlier quoted context omitted.
I don't think that Tanenbaum was being completely serious. The point is to put the value of that copper (and the cost of replacing it in the event that it is damaged) into perspective.
He certainly wasn't. If you read his political blog ( http://electoral-vote.com/ ), you'll find this sort of sarcasm is his hallmark.
My favourite Tanenbaumism, while I'm on the topic: Aircraft carriers are modular. If a toilet gets clogged, it doesn't start launching nuclear missiles.