I've spent an obscene amount of money in the 3 years I've had prime. I've definitely saved money on the necessities, but it's easy to one-click the impulse stuff. The subscribe and save stuff is great too. In my opinion, Amazon Prime is the best deal in online shopping.
I routinely find items priced lower someplace else online, but the difference is usually less than the cost of shipping. I go out to stores much less than I used to, and when I do I compare everything to Amazon. It's not uncommon for me to purchase several items from my phone and walk out empty handed. It's getting to the point where I mostly only go to stores for food and things that can't wait a day.
Sooner or later brick and mortar retailers are going to experience massive fallout from Prime.