Costco is great for rental cars...unbeatable pricing. We just got back from New England and rented a midsize car for 10 days at the Portland, ME airport for $168. I get a family discount at Enterprise, since one of my sons works for them, and Costco beat that price. Last summer, we went on a month long road trip to Canadian Rockies and Pacific Northwest and saved $900 on the car by renting through Costco. We travel a lot, so between rental cars, vitamins, and eye exams, the Costco membership pays for itself. I wish the travel destinations weren't so limited....those deals are probably great, as well.
I got a year of Prime a couple years ago at a discount and found we didn't use it that much, so I let it go. I am quite organized, so my bf and I place our orders together to get the free shipping. I mostly use Amazon for specific items that I don't feel like driving everywhere to find.