What's the cheapest thing you had bought that by the end of its usefulness made you say "wow, this was worth a lot more than what I've paid for!"
Mine... My Xbox 360 slim only costed 129 euro back in 2012 and to this day still work like brand new, you would think that the disc drive would stop working but no. Never had the need of open it or clean it's insides. Still great, I just don't use it anymore since I feel it's outdated and loading speeds are better nowadays.
My father got a toaster at a garage sale back in the 1970's. That was the toaster I grew up with. When I was moving out, my parents happen to be replacing it, so I asked for it. I did some research and it is a GE toaster from the mid 1950's. I have used it for the past ten years and it's still going strong. It's maybe a bit small for some slices, but it's hard to argue with 70 years of near continuous service.
This reminds me that every night I set the alarm on the alarm clock next to my bed. I bought this alarm clock in 1991 in a Caldor store for less than $10. It has a little light bulb in it that I've changed 3 times.