Here's my advice - if you can't get it for cheap, then don't do it. The margins on them are HUGE. I work for a good sized bank, and we looked at offering extended warranties (for cars, but the economics are the same). When we did the analysis of the product, the expected payouts were incredibly low - less than half of the price that is charged. None of us felt comfortable that the product was really in the customer's best interest (i.e. we'd be making too much money off of it), so we elected to not go into that business.
Also, from a personal front, my dealer offered me a "deal" on one of these (plus prepaid maintenance for 4 years). They quoted me $4500 on it, and I just laughed and told them to beat it. They came back IMMEDIATELY with a revised quote of $2500. Without batting an eye. Which just proves my point about how much margin they were going to make. I passed on that number and they came back AGAIN at $1900. The dude was desperate. I have no objection to the dealer making some money - we want them in business long term. I just prefer not to get bent over in the process.