You do know, right, that these are almost always pure profit for the vendor. This is why sales staff are encouraged to push them at every opportunity, and may even be canned for not selling enough.
There is a devastating yet polite rejoinder for pressure to buy an extended warranty: “If you think an extended warranty is in my best interests, then you must think this product is going to fail shortly out of warranty. Therefore, are you saying that this is a very unreliable product prone to failure?”
The usual response is hilarious. “Well, sir, I don’t mean that, just that, in case something does happen, you’d be covered.” Have no mercy: “Right, but this is supposed to be reliable. Either it is a good product or it isn’t. A good product doesn’t need me to buy extra warranty because odds of failure are remote. A lousy product isn’t worth buying to begin with. Which is it?”
Now, if they answer you honestly, have mercy: “Honestly, sir, they nearly never break. But my job requires me to offer this to you, and I can see you aren’t interested, so I’ve done all that is needed. Shall we ring you up?” If they have the candor to do that, treat them well. It takes large nads to come out and say that. If you’re really impressed, buy extended warranty just to help the guy or gal along. You never know when that karma might revisit you.