Everything that is under you. Shoes, mattress, bike, car, desk chair etc.

Cheaping out on the above will cost you more in hospital and physical therapy bills.

PC power supply.

Never, ever skimp on a power supply. Get one from a reputable brand and with a rating above what you may actually need.

A failed PSU can in principle wreak havoc on any other components in the system, many of which are far more expensive than the PSU itself.

Toilet paper

A computer chair.

As I get older my back is really happy that I spent a bit more on the chair I spend almost all my time in.

Disclaimer: my wife has a chronic neck injury.

Car! We've had Renaults for years, but last time we went for a BMW and the difference is night and day. My wife had to do lots of stretching exercises just to go and buy bread. In the BMW she can happily drive 5-6 hours with no (extra) discomfort.

Laptops that are designed to support Linux

I totally get why you might not but for me, quality underwear has been a great purchase. They last longer, breath better, stay put, and synthetic ones are washable in a sink in a pinch when traveling(I mean they all are but these dry really quick)

Office chairs are important, but people tend to overlook the rest of their office ergonomics. If you work at a computer you should spend money on an adjustable keyboard tray and monitor arms. Then buy a good ergonomic keyboard and vertical mouse or trackball to go with them. My back and wrists used to get sore by the end of the day. That hasn't happened since I upgraded my gear.

Coffee beans for sure (gotta love freshly roasted specialty beans!), but also vegetables (organic & local are the best). Oh, and also headphones, for sure.

To me these are all totally worth it because the jump in quality is very noticeable. After a certain price point, though, the law of diminishing returns kicks in hard

Anything that connects me to the ground. Shoes, Mattress, Tires, etc.

Underwear and socks. PC desk, don't trust a 50$ folding table with your midlife crisis gaming rig.

Pretty much everything, nowadays.

I came across a saying "Buy nice or buy twice" and that resonated with me. Another variation I have seen is "Buy once, cry once".

Getting cheap trash that will fall apart in a few months that you will have to eventually re-buy isn't going to help, but that doesn't mean you buy gold-plated or diamond-encrusted items. Spending a little bit more for most items usually gets you something that will work better, last longer, or both. Good quality stuff is usually backed with good warranties too.

I spend my time researching to see what product is the best for me, look for deals online, or even buy used if I have to.

Sushi

Any tool I'm going to use more than once.

Never skimp on what you apply ON or put IN your body.

Sandpaper. Cheap sandpaper loads up, and wears out so fast that it's never worth the savings. Spend a bit more and it will last 3 to 5 times longer.

Good cookware. Non toxic stuff and good knives.

As some have mentioned, OEM car parts, particularly anything electrical. It’s just not worth the money saved on cheaper aftermarket parts that may not work even though they are new. It often leads to unnecessary troubleshooting and sometimes even more parts, only to land right back where you started.

Stuff from locally-owned stores. Tools, supplies, car parts, food... if the markup isn't egregious, I'll always try and get from them before a big box or online. Not only does it help the owners, but they're frequently knowledgeable and can sometimes work stuff out for you.

Helmets

Honey and Olive Oil. Not always, because the good (i.e. real) stuff can get pretty expensive, but for uses where it's centre stage, the difference is massive.

I use the saying quite often: "You can buy something nice, or you can buy something cheap and then something nice."

PC power supplies. God, do not cheap out on them. That and a bed mattress. A good sleep is more important than money.

Not a product, but tattoos.

It hurts to hear the price from some artists, but you absolutely get what you pay for.

Hot dogs. I do not trust cheapo hot dogs.

Also, I rarely eat pop-tarts anymore, but when I do I get the name brand. I've never had an off brand pop-tart that wasn't complete garbage.

Dildos. I need one that has some mass and I can use as an improvised weapon when shit gets real.

Wood screws. Makes life so much easier than using cheap screws

Food. I’ll give you everything else I own for food if I really need it.

Headphones. I first used some cheap ones and then switched to Bose. The difference was significant. Never again cheap headphones.. Also my ears thank me because I can listen to music with lower volume than with the cheap ones.

I'm bias due to my profession, and regularly get attacked for this point on the Internet by people who think they know better, but glasses.

My eyes aren't even bad, but when I wear them, holy shit is there a difference between the high tech new stuff and basic lenses.

Anyone that tells you online glasses are just as good has never had a 600$ pair from a real (not chain) optical. Anyone who says they have got ripped off by Pearl vision or LensCrafters.

A bicycle