A bicycle. No gas to pay, no parking fees, no insurance, and I can do most of the maintenance.

• Epson Ecotank Printer

Has ink tanks so money isn't wasted on cartridges and the printer is actually initially expensive unlike those printers that make money back on ink catriges

• Hammer Drill with the proper bits

Makes it easier to mount shit to bricks, goes in brick like butter if you're using the right drill and bits

I recomend Ryobi Hammer Drill & Bits

• Air Fryer

I've stopped using my oven and only use it rarely for things that I don't want blown apart thst I can weigh down with a fork or spoon like Pizza for example

• Refillable Japanese brand pens and mechanical pencil

I recently got these to aid in Japanese study and refillable pens are more economical in the long run

And Japanese brands go hard on the quality of stationary and I got introduced into the cult of stationary obsession with this

I'll edit my comment if I can think of anything else

I'm going to say my $50 charcoal grill. I've had more propane grills fail on me in 5 years, and charcoal grill keeps going. I know its terrible for the environment.

House insulation.

I live in Australia where the minimum insulation required by law is a long way below inadequate, and many cheap contractors go below the minimum because it's so hard to prosecute them.

I already had solar and a house battery, so the next obvious step was replacing the insulation. With my already very low electricity bills I cant say that it literally paid for itself (although it would have without the solar and battery), but it has made the house so much more comfortable. On some summer days, the AC would be using 7kW and barely keeping the inside temperature down to 30°C/85°F. Now it uses 3-5kW and the whole house stays comfortable.

Also, finding and patching the massive gaps from the previous "landlord special" house extension made a huge difference to the temperature of that room, and explained how lizards had managed to get inside.

Camping hammock, it's what I sleep in most nights. My body complains when I have to use a mattress

My Casio A 168 - I like watches and typically I would opt for more expensive ones but I still marvel at the amount of watch you get for this kind of money. The design is great, very comfortable to wear, very precise and has a very good battery lifetime and background light.

Someone else already mentioned a safety Razor.

My iron pan - much healthier, more ecological and will last longer than I will ever live.

Obviously my bike. Saved so much money on it. Although I still need to figure out what I should do with my very rusty chain. Should I replace it?

50ft electric plumbing snake. Cost $60 and saved me $200+ bill first time I used it. I've used it for friends and family as well, making its value well over 10x in savings, not just my own.

I bought a big pack of eneloop rechargeable batteries a decade ago and they are just within the last year or so starting to fail.

Two pairs of black Carhartt cotton duck overalls I bought in 2010 and 2011. One knee is blown out but they are the softest most comfortable clothes I own. I still wear them once or twice a week, wash on hot, dry on hot. These, a Dickies pocket T shirt, and 15 year old 14 eye steel toe Docs are the 'uniform of the day'. Other than a few nice suits and some shorts, I'm pretty much not interested in clothing. The suits were bought for corporate recognition and I work from home otherwise.

Put 11.6 KW of solar on the roof. I'll hit break even next year. Should have 15-20 years left of use.

I guess my bike? Have saved loads of money on bus tickets and it's much more reliable too.

Sewing machine pays for itself quite quickly as paying a tailor to repair your clothes is like 1/3 the cost of a brand new sewing machine, so just repair like 3 items of clothing to get your money back.

I got a hot air rework station with a soldering iron many years ago.

The things I've repaired with it are so numerous, I cannot even recount them all, but here are a few:

• an assortment of gaming controllers
• a ghetto blaster from the 1970's
• a few gaming consoles (Xbox 360, PS3 "Fat Lady")
• retro technology (at least two 3Dfx Voodoo's and a rare Abit motherboard)
• a full-metal eBook Reader (Sony PRS-505) that will probably survive an atomic fallout
• a Panasonic broadcasting camera from the 1990's (because it looked cool and I wanted it to work)
• a few LCD monitors

Even though some of that work was just replacing old capacitors, I have saved so much money by buying "broken" stuff and fixing it up. No regrets. Over the years, I paired the station with a hotplate and a solder sucker and now I could probably open up an electronics repair shop. But I mostly do these repairs for fun. Fixing things calms my mind and soothes my soul.

First thing that comes to m8nd is my Pitbull head shaver. I s(h)aved several hundred euros on simple head shaves, 2 minutes a time.

Used Wacom Cintiq 21UX I got off FB marketplace for like $300 (MSRP went for $1500+) about 5 years ago. No new drivers are being updated or released for it because it's so old, but it still works great. I've likely made back what I paid for it in art commissions since then.

Setting up a fully automated system to download, track and organise … eh … Linux distributions …onto a NAS under the stairs. I used to subscribe to a bunch of services that would … eh … provide access to all sorts of … eh … Linux distributions … for a flat monthly fee, but I realised that I often was only really interested in one or two specific Linux distribution so I really didn’t need to pay for these services.

Now I just download the … eh … Linux distributions that I actually want to install. It also prevents my kids from … eh … endlessly installing different Linux distributions. Not really a productive use of time.

My motorcycle has paid for itself many times over in terms of the enjoyment I get out of riding it. It's something I can recommend to anyone, and lets you see the world in a way most people never will.

• Smart Lighting - My mum replaced most the lightblub in our house with Philips Hue. Nearly decade on and still using them which as an Autistic, I love that I can tweak the lighting to however I want from an app and compare to regular lightbulbs, it doesn't give me as much sensory nightmare as I find some of the lighting to be really harsh and distracting.
• Noise-cancelling Headphones - Often use it if I'm in sensory overload, walking as I tend to listen to music as well as being on the bus to distract myself which otherwise, I start panicking how full the bus is.
• Desktop DAC & Bookshelf Speakers - Always find changing volume on OS itself to not be perfect as it too low or high for my liking. I can simply tweak the volume knob of my Desktop DAC to get the volume just right. Also great way to listen to music

A local NAS for storing all my files, especially if you consider all the value I deprived from Google and Microsoft by not engaging with their cloud bullshit. Even if you don't, I paid like $500 CAD one single time for a 16 TB server hard drive and $300 for a consumer hard drive I'm using as an offline emergency backup. Meanwhile just 2 TB of Google Drive costs $139.99 CAD per year. I wasn't able to find pricing for 16 TB but assuming it scales linearly (like if I had 8 2TB accounts since Google seemingly doesn't offer any higher capacity for individuals), that would be $1,119.92 per year. Even factoring in the hard drive enclosure and the server itself, they've paid for themselves in literally half a year. That's saying nothing of the kind of internet connection I would need to match the read speed of a mechanical hard drive on the local network. I could literally upgrade my entire house to 10 gigabit with the money I saved.

I have two 10,000 liter water tanks in my basement that I use to harvest rainwater, and another 2,000 liter tank on my roof. From October to around May I close the city water and use only rainwater. I’ve been doing that for a bit more than 10 years now, and it paid for the installation cost in about 4 or 5 years. I also have solar water heaters, but it’s hard to tell how long they took to pay for themselves because I also have on-grid photovoltaic panels for energy generation. My energy bill is about 1/6 of my neighbors’, and the photovoltaic panels paid for themselves in about 5 years as well.

When you are replacing a water heater, always get the biggest one possible. Nothing is worse than being the second person showering, and you run out of hot water halfway through. It used to happen to me every day.

Then we had to replace it, and a bigger one wasn't that much more. I asked myself if it was worth $100 to never have a cold shower again, and then got an even bigger one than that.

Haven't had a cold shower since.

Hair clipper. Paid for itself in two uses. It's been years.

Battery charger.