my entire shopping is on Amazon. Sometimes, I go to store, but end up buying stuffs off Amazon.. , there is a huge price difference anyway.. some of the items gets expensive on Amazon, coz few sellers normally don't keep up with the pricing and old price may still be lingering, some unfortunate may end up buying those stuffs on old prices. Other than that, Amazon is notorious for keeping price low.
I signed up with them 5 years ago, when they had no Prime Video and there was no taxes. Now, they've Prime Video but hecuva taxes on items you buy.
Btw, your amazon prime is only for Prime eligible items, not all sellers are prime eligible, meaning you still have to pay for shipping etc for those non-primes. Ever since, I always make sure I buy items by seller as Amazon only, any other sellers is rare chance for me.
If you are not a frequent buyers on amazon, I don't think you need to sign up with them, but if you buy more often there, 79 bucks a year is nothing. It's like 20 cents a day.
I highly recommend Amazon to everyone though and think it's very much worth.