My mother-in-law’s computer blew up recently, just after the warranty expired on it, and she was told it would cost more to repair than to replace. She was upset that she hadn’t chosen to buy a protection plan when she purchased the computer, but I told her that the math didn’t work for most of those plans.

There’s a post today in NPR’s All Tech Considered blog that wraps up the conundrum many consumers face when it comes to buying expensive electronic warranties. Consumer Reports neatly explains why this is such a bad idea: Store profit margins on extended warranties are 50 percent or greater! This almost as big of a skim as the $100 HDMI cables some big-box stores try to get you to buy with a new flat-screen TV, with a claim that the cables will improve your picture quality (they don’t — that’s not how digital signals work).

Of course, what do I know? A few years back, I declined to get the $150 hurricane insurance on a $1,200 vacation rental in the Outer Banks, because I did the math and thought the price was absurd. Sure enough, after three days, the island got evacuated for a hurricane warning, and I was out about $600. But that was the only hurricane to strike the OB in the last several years, meaning I lost odds of at least 1 in 200 or so.  It reminds me of something a pit boss once told me in a casino: There are sucker bets because sometimes, the suckers win.