I'm picking up a 2011 with just 22,000 miles on it for $18,500 at a Ford dealer. Great shape, clean CarFax, regular service at a Toyota dlr. The dealer want's to sell me a 3-ur B to B warranty, but I said "No, let me sleep on it first." It would bump my payments more than I want. BUT, I will take it to a Toyota dealer (I'm buying it at a Ford dlr) on my first day off and have them do a full service on it. My last Prius, '07 had 115k+ miles before it was wrecked (cost more to fix than it's worth), and I had no problems whatsoever. So, would it be worth it to get a warranty? I went over it pretty well and it's pretty darn clean.
It all depends on your comfort level. Toyota has a pretty good track record for maintenance. That said, I've always been more comfortable knowing I've got coverage. I recommend you get in there and do some more negotiating to get the cost of the B2B warranty down. The dealer should be willing to work with you at least a little bit.
You didn't say how much they were asking for the warranty, but I'm not in favor of financing a warranty simply because it ends up costing that much more. And if it's going to raise your payments past your comfort level, they might be asking too much for it. The car has been driven less than 5,000 miles a year, so it's almost brand new and I can't imagine what would go wrong in the next 3 years. There's also still the manufacturer's 7yr/100k warranty on some of the major items. Did you buy a warranty when you got your '07? If not, then I suspect you're considering it now simply because the car is an '11.
Over the life of the loan, 48 mos, the warranty would cost over $3000, putting my payments past my comfort level. Even half that is pushing it. I know they are in it to make money. I'm taking it over my Toyota dealer for a full service next week, just for my peace of mind. Even though something could go wrong down the road, I could put that extra money away incase something does go wrong. And I can't buy the warranty out-right, can't do it. So yea, I'll just go with no warranty, put money away, and hope for the best over the next 3-4 yrs. Besides, it needs tires soon!
you've still got 4 years and 78,000 left on the hybrid warranty, i'm sure you'll be fine. all the best.