This argument rates right up there with Ford or Chev, gas or diesel, etc. If you have the full 8k right now they yes put it in the bank. If you need to finance the 8k then ask yourself what you can afford now to fix if it goes bad. Engine, trans, fridge, etc.
Yes, lots of them do their best to get out of it but you also hear a lot of folks that got more than their money out of it. Look at one that is an exclusion type contract. It lists what is excluded, easier to figure out than what all is covered. Also get incidental damage, if a covered part takes out a non-covered part they will also cover it.
Is it a good deal? Depends, auto and home insurance aren't very good deals, well until you need it. It often boils down to peace of mind. Keep researching and you'll find both arguments strongly endorsed. Good luck with your search.
