I've never bought an extended warranty, but the finance guys have always tried to talk me in to it. My favorite conversation went something like this:

Finance Guy (FG): Are you interested in an extended warranty.
ME: Not really.
FG: It would only add $3,000 to the total purchase.
ME: $3,000?!? Yikes, no thanks.
FG: Well, how about $900?

That just came off so shady that red flags were dropping from the ceiling.