As far as the good cheap items go it would definitely be my earbuds.
I spend only a few bucks on them but man do they last. I constantly have them on and use them throughout the day and they last a long time. I don't mind spending the money on extra backup pairs just in case my dog chews them up or something. They definitely even work and sound better than some more expensive pairs I've had over the years. Last longer too.
As for the expensive useless item that would probably be the Japanese 3DS I bought. I only bought it to play I think 2 games? Damn region locks.
Cheapest useful thing: Almost anything from Dollar Tree, such as cookie pans, chocolate, birthday cards, cleaning supplies, etc.
Most expensive useless thing: Bachelor's Degree in Psychology. I can't do much with it unless I go to grad school (which I will be doing)
cheapest - little clip on lamp for my bed
expensive - hmm. I once accidentally bought two pairs of ray ban sunglasses on amazon. Only wanted one, and got a refund on the second. Near enough £200 on a stupid mis click.
Cheapest thing: Headphones.
Most expensive thing: An Xbox 360 controller that I wanted to use with my PC. Sadly, it came without an adapter and due to Xbox's lack of popularity in my country, I can't find a non-bootleg adapter here.
Oh, I have a few cheap items that proved its value over and over again.
This model of toaster oven that the family bought way back in 2004. Yes we have a much older model and that oven lasted until 2016. Let me tell you, my family pretty much used that thing several times a day, which mainly replaced our big oven other than really big jobs. It did fizzle out in 2017 but it was so reliable that we bought a second one for daily use. Let me tell you, it made otherwise barely tolerable meals to quite tasty. And it didn't heat up the entire house!
A power bank that I bought as an impulse buy for my cosplay but now I'm using it on a daily basis. Seriously, gives me peace of mind and has saved me on many occasions.
I also bought myself a plain body pillow and oh man, that pillow has saved me from many sleepless nights. From being a source of extra comfort to being an additional source of "coldness" on a hot night, for $10 over 3 years, man, I could not believe Target sold it for that cheap.
Alright to the useless category:
An icemaker. Honestly, I don't remember why I bought it. I think it was supposed to be something back in college where I could put really small drinks to keep cold for my dorm. However, I have never used it and sadly, that was about $200 down the drain.
My old Toyota Camry. Actually, it wasn't useless per se, but it could have gotten way more use. Basically, it was my first car that I got when I was 16 and I had to leave it behind when I went to college. Then what happened was that my brother got into an accident with my car (not his fault) while he was in college. Also, this was when I learned I could have brought my car and just leave it on the off-campus lot while I was dorming. Friggin school not telling me about the off-campus options.
My Physics Degree. Okay, I wouldn't say it was "useless" per se but I felt that I probably should have picked another major to study. Yes, Physics was very interesting for me but if I wanted to justify my university tuition, I probably should have stuck being a Computer Science Major and also perhaps majoring in Applied Math. While it's debatable whether or not my Physics degree has hindered me, I end up working as a Software Engineer and saved myself the stress.
Let's see, what am I an expert at? Sleeping I suppose. I like to consider myself an expert at some games, like Elder Scrolls, knowing heaps of information about the games and lore.
Now what is the cheapest most useful thing I've ever bought?
Like Piko there's a few for both categories...
My Switch case, cost me only like $20 and it's so handy to put my switch into my bag and carry it around without having to worry about it.
I bought a file organiser recently, also for $20 and it really helped me get my documents in order, they were just sitting in a box all over the place before that.
And I would have to say the keyboard I bought to replace my last one is useful just because it's probably something I use for hours each day, only cost me $7
For the most expensive useless things I've ever bought?
Usually games, I'll spend $70/$80 on a game and barely play it sometimes
I spent about $90 on some markers a couple months back, I've only used them once or twice, but I have been trying to make them more useful by actually using them more.
I kinda want to say my fridge ($200+) and my Xbox One ($300+) but they've only lost their usefulness in recent times, my fridge broke recently so it's nowhere near as useful and I haven't touched my Xbox in almost a year. But before then I'd use both all the time and they were very useful.
I dunno about cheap useful thing... all the useful stuff I have either wouldn't count as super-cheap or someone else bought them for me. Ah no wait! I just thought of something. A HEADPHONES ADAPTER FOR MY STUPID HEADPHONES JACK-LESS IDIOTIC STUPID PHONE (the phone so stupid I called it stupid repeatedly, woo). I've worn headphones constantly when walking around various campuses/work since I was 16 (I'm 36 now) so not having music playing while wandering around outside is weird and unpleasant and I do not like it so the adapter was an emergency buy when I inherited this stupid phone (stupid count: 6). Super-cheap but also a life-saver.
Expensive useless thing: my X-Box 360. Not only did that thing injure me when I tried to pick it up the first time (pulled my shoulder partway out of its socket. No worries, was easy for me to put back but was not very pleasant!) but I only used it for like Dance Central or whatever at most 10 times and literally nothing else (so yeah, that means I also bought a Kinect with it, increasing its useless expensiveness). Now it just sits there next to my telly looking pretty (I skinned it so at least it's not uggo and useless). I'd sell it but I can't be arsed.
Cheapest useful thing I bought and most expensive useless thing? Wow, this is actually a tough one.
I think in terms of cheapest useful thing, I'd have to go with my TUL hole punch. It was only about $40, and it's allowed me to make my own pages in the TUL notebook I have instead of buying the premade ones. It's basically paid for itself at this point, and it's allowed me to be more creative with my bullet journal. I also haven't had to make regular trips to Office Max to get the premade pages, which at this point, would've cost probably three times the cost of the hole punch, give or take.
The most expensive useless thing is a little harder for me to think of. I usually try to avoid buying things unless I know I'm going to be using them. I guess for this one, I would have to say my Google tablet, I believe it's the Pixel C? I forget the exact name of it, but I got it about 3 years ago when I got my Google Pixel phone so that I could have a newer, larger screen for my tablet. (I had the Nexus 7, which still works fine and all, but it was smaller screen and I had to get a separate Bluetooth keyboard for it. My mom uses the Nexus 7 now and it works like a charm still.) I got the tablet for school though since my laptop at the time had a failing battery and always had to be connected to an outlet or it'd die within 15-20 minutes, give or take, and that wasn't really ideal for a classroom setting when my classes were an hour and 15 minutes to 3 hours, depending on the class. The tablet was also a lot lighter and easier for me to carry around. Now that I've graduated, I'm not really using the tablet much at all and it's just sitting around taking up space. I don't have the heart to sell it because I like to believe I'll find a use for it, but I just haven't gotten there yet. I would really love to be able to use it as a drawing tablet instead of spending the money on an actual drawing tablet, but I'm not quite sure how I'd go about doing that.
(04/09/2019) - If you were a character in a show, what kind of show would it be?