Old cars 1798
You might think that, but I've more than paid for the extended warranties I've put on vehicles and a heater-air conditioner (and I pay more initially because I buy the zero-deductible version). I suspect part of it is that we keep our cars for a long time. Right now we've got a '93, a '96, and an '01. If we traded cars more often, more like the average, we'd never run out of original warranty.
As for the heater-air conditioner, we just got our third replacement for the circuit board. We've owned it for 6.5 years and we have a ten-year warranty on it. The warranty cost less than one replacement board (the first replacement was on the regular warranty, I think). This is a known flaw now, but it wasn't recognized at the time we bought.
Old cars 1799
And much as we hate to admit it it (and I'll always have a soft spot...
We also have service contracts for heating and cooling at both houses, if only to be sure someone besides me replaces the filters in the ceiling-mounted returns (twelve-foot ceilings). Those contracts cost less per year than the twice-yearly service calls. I save a little more because I provide my own replacement filters, bought by the dozen on the Web.
However, we don't buy extended warranties for anything else. We'll take our chances with computers, TVs, washers & dryers, refrigerators, cell phones, telephones, speakers, houses, etc. Those warranties aren't worth the money.
-- Mary Shafer Retired aerospace research engineer We didn't just do weird stuff at Dryden, we wrote reports about it.