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 Still great, I just don't use it anymore since I feel it's outdated and loading speeds are better nowadays.
I keep an old Ozark Trail Hobo Tool in my overnight bag. I can't tell you how useful it's been when traveling and ending up at a hotel somewhere getting take out to have an actual knife and fork.
I got a full set of silverware for backpacking that collapses down to about the size of those folding reader glasses (plus a little hard storage case just like the glasses). It’s a spoon, fork, knife, and chopsticks. I think I paid $6 for the set. Not super high quality, since the focus was on weight and utility, but definitely does the job.
I don’t use it much anymore, but it was great for lunch at work, and is good when traveling (staying at hotels and getting takeout - no plastic trash!). I mostly keep it in my overnight backpack so it’s available whenever I’m not home and I can’t forget it.