My washing machine. What a wonderful time and labor saving device. And talk about something that “pays for itself”! Best investment any homeowner can make.
A few of the games I bought from Steam for my PC. I paid $2.50-5 for some of the better ones and have gotten hundreds of hours of enjoyment from them.
My Merrell hiking shoes. They’re waterproof and ventilated, and I wore them hiking through the U.S. Southwest, then through Spain, then two trips through Southern France. Even back home, they’re the only shoes I wear, except when I’m wearing my tux. They are the ONLY shoes I’ve ever worn that don’t give me blisters, no matter how many miles a day I walk.
And my kitties. $45 adoption fee to the shelter, food, vet visits, litter, toys, etc., etc., etc. What I get in return is priceless.
My two big boy cats were already neutered when they were surrendered to the shelter so they were only $15 each, which included all shots. And my sweet sweet 11 year old insisted on paying for one of them out his own savings and managed to guilt his older brother into paying for the other, so they were free really! They make me happy every time I see them and double happy every time I pet them and supercalifragilistic happy every time they purr!
About six years ago I bought a couple small pots of Gloxinia “Evita” for $10.
The rhizomes have increased in number every year, and now I have enough for at least 75 pots.
I’m rich, I tell you! RICH!!!
I will second that on my cat. We got her at a shelter and paid $50 for her. Add in the vet bills for a grand total of $550. The love I get from this wonderful cat is owrth more than I can imagine.
One of my cats was “free”, because he showed up in my yard shortly after 9/11. I didn’t think he was fully grown, but it turned out he was parasite-ridden and malnourished, and was between 18 and 24 months old, per the vet who looked at his teeth. So, I call him the “millennium kitty”. 
My other kitty was adopted from the shelter, and the shelter happened to be doing free adoptions that month, so I didn’t have to pay anything to acquire her, either. She made up for it a couple months ago, when she pulled a flyer off my bulletin board with her mouth and I couldn’t find the thumbtack, so I rushed her to the vet, and $216 later (which did include a bag of catfood), they said she hadn’t swallowed one after all. I still haven’t found that thumbtack! They took an x-ray and the vet inspected her mouth. And did she ever hiss when the tech lifted her tail to take her temperature. :smack:
Definitely our pets. They all give back more in love and affection than they cost.
From a purely monetary view, we have a vintage Sting Ray Corvette that even in its needing-many-repairs condition is probably worth four or five times what it cost when new.
I have a cast-iron pan that I got for nothing. It had been left behind by a former tenant in an apartment we rented over 45 years ago. I use it all the time.
My dogs, of course. Their adoption fees were miniscule compared to their actual value
My lemon tree. So many lovely lemons, year in year out.
My bread machine. So many lovely loaves of bread, warm and fresh in time for lunches over the years
My motorbikes. Way more pleasure and hours of enjoyment than their ticket price would suggest. And in that theme - motorbike helmet. Price seems a little much, but it saves your brains! (value may depend on quality of brain : cost of helmet though) 
My home. Bought at the right time, so monetarily it’s worth more, but more importantly - the big lifestyle change it required was everything I’d dreamed of and so much more. It’s worth double what we paid.
A set of knitting needles. For a tiny price, they have created many gifts and provided hours of entertainment
A moving trolley. Saved my back so many times. Sturdy, cheap and endlessly useful!
Good tea. For only a little more than the crap stuff, I can have a cup of tea that is so rejuvenating I’m surprised it isn’t prescription-only
Exterminator service every fall to keep those blasted Asian lady beetles out of our house. Our first several years here were miserable as we tried to follow the Extension Department’s advised strategy of “Oh, just vacuum them up occasionally.” The damned stinking things oozed out of the walls of our very old home from October through February, landing on us (and biting) when we were sleeping and flying out to hit us in the head when we least expected it, leaving their rancid little poop trails on the walls. Gah, it was horrible. We now pay around $200 to have the exterior of the house sprayed every fall with some toxin, and I’d be willing to pay much more than that for a winter’s worth of peace.
Bubble gum from around 1960.
Don’t have the gum any more, but those little pictures of Hank Aaron, Mickey Mantle, and Roger Maris are kinda nice.
13 years ago, we were getting ready to move, and along with 2 cars, we had a motorcycle to get 700 miles away. We had no luck finding a UHaul that would work, but the rental place had a utility trailer for sale. Even tho I hated to do it, we bought it with $800 we really couldn’t spare at the time.
Holy cow, has that trailer been a wonderful thing to have!! When we lived in Jacksonville and our daughter was getting ready for college in Orlando, we hauled her stuff in 2 trips. My husband’s folks borrowed it to pick up some furniture from out of state. We used it countless times going to Lowe’s or Home Depot for building materials. It made at least 8 trips from Jacksonville to southern MD when we moved 9 years ago, plus it hauled our stuff from the storage unit to the house when we finally took possession. And then there are all the trips to the dump with construction debris, yard waste, and some of the weird stuff the previous owners left behind in the sheds. I’ve also used it to pick up stuff we’d stored at my mom’s place. And most recently, we’ve hauled gravel for some landscaping projects.
Best $800 we could have spent.
Amazon Prime. I’ve used it so much I can’t believe I haven’t worn it out.
Our dogs.
My son is into lego. Like, really into lego.
I ended up as the default goto person whenever he had some that were stuck together. After using knife blades, tweezers, and other unsafe methods I found out that lego makes these things. All my lego rage is now gone.
(Tip: Buy two or more. You need to use two together to seperate tiny bricks.)
I only paid $64 for my marriage license, and got a whole new life in return.
A $100 Black & Decker tool set from Wal-Mart. Not the highest-quality stuff they make, but I’ve gotten a ton of use out of it. So far, there’s not a tool I’ve needed that wasn’t in there.
I hope Sony doesn’t read this, but I’ve gotten far more enjoyment out of my PS3 than the $350 or so I paid for it, especially since it doubles as a Blu-Ray player.
I have a Galanz microwave that I bought for $50 at Best Buy back in 2003. The thing just keeps on ticking and is showing no signs of slowing down. It even still looks relatively new. I had just moved into a new place on my own and needed a cheap microwave, anticipating that I’d buy a more expensive one later on. Never needed to.
I’d also say my cats, but the love you get from pets far exceeds any dollar amount.
My wife bought one of these at a yard sale for ten bucks Black and decker coffeemakers was recalled by Applica . I was looking online for a manual and it turns out the product was recalled, they are sending us a new coffee maker and a new juicer. Not bad for a ten dollar investment.
I bought 27K rounds of 7.62X51 about 10 years ago. For between 10 and 15 cents per round.
I could sell it and make a small fortune. But I don’t want to sell it.
I agree with this. My dog is priceless. I had to take him to the emergency vet clinic this past weekend for what turned out to be liver inflammation and they kept coming in with estimates on the next test they were going to run. (Visit is $95, Sign here Blood tests are $150, sign here, X-ray is $125, sign here) After that one I explained that whatever it costs to get my dog better I am going to gladly pay so none of these estimates are necessary. I could spend $10,000 to keep him alive and it would be well worth it.
Absolutely agree. (Technically I got mine as a gift, but even if I had paid for it, the return on the investment is much greater than I was expecting.)
Under Armour gym bag - I had been bringing my stuff to the gym in old backpacks and shopping bags, and it is such a wonderful luxury to have a big, high quality, compartmentalized bag to throw all my stuff into.
Cover for my Kindle - I love being able to throw my Kindle in my purse and know it won’t get scratched.
Eyebrow threading - It seemed like such a waste of money since I could just tweeze my own eyebrows, but my stylist does them so much better than I ever could.