Prime has saved me a ton of cash in the last 2 weeks!
I had a small crack in a rear tail light (light still functioned and was fully enclosed) so it failed inspection, even though it was cracked in 2010 and wasn't flagged. Repair shop quoted me $140 parts+labor, I found the part on Amazon for $60 and got it in 2 days, it was literally a 2 minute repair. That alone was worth cost of membership.
Then I just randomly got a check engine light, got a free scan from AutoZone turns out I just need a new gas cap. $6 on Amazon, shipped. It'll be here tomorrow. I bought a OBD-II Scanner for $16 just so I can read codes myself now.
You name it, I buy it on Amazon first: vitamins, shampoo, shaving cream, shoes, clothes, guitar strings, books, cameras, electronics, tools, the list goes on. I get exactly what I want, the first time. And if not, painless returns.
Just go to Amazon first, and look at how much you save over retail (even if you factor in sales tax) and hassle of not driving all around town looking for something in particular. Hell I check Amazon first just for the reviews, even if I am going to buy it retail.
Best $80 I spend every year. And I didnt even talk about the streaming!