Medicine. The house brands and generics are the exact same, tested the same, made the same.

I buy a lot of generic or store brand stuff. Usually I'm comfortable doing this with things that have been around for a long time like bleach, laundry soap, and basic foods. I assume that it is not difficult to do these things so anyone can make it and there's little if any difference between brands.

On this topic: I heard once that you should first buy cheap tools. Use them until they break and then decide what you want to improve about those tools and buy better ones. Often those first tools never break. This seems like pretty good advice for most things.

Cars. Expensive cars require more frequent and complicated maintenance and repairs than cheaper cars. They over engineer them on purpose in order to make it unreasonable to maintain them in the long run. They don't want their brand sullied by old versions of their cars driven around by poor people.

Water. At least here in Denmark. Bottled water is less regulated than tap water.

Dogs, rescues are just as doglike and mostly free compared to the Hapsburg simulator known as breeding

In the UK, baked beans.

In my work we did a blind taste test of 10 different brands of baked beans, with participants ranking them in order from best to worst. The name brand options such as Heinz, HP, and Branstons ended up in the middle, with the cheaper options from Aldi and Asda being the best. The most expensive beans were from Marks and Spencer and were voted the worst ones.

If you're paying more than 50p a can its not worth it.

Speaker wire. Expensive speaker wire will not sound any better. You could use a coat hanger and get great sound. Tip: every few years cut the wire ends and expose fresh wire to use. Over time the wire can oxidize if I recall correctly.

My rule of thumb: Buy the cheap one. If it wears out or breaks, buy the good one.

Buying operating systems is not worth it. Just use Linux.

I personally do not find expensive wine and liquor worth it. That obviously don't mean all cheap wines are good, but I find the percentage of bad wine I had at $50 - $70 range is pretty much the same as wine around or under $20.

I find the best way is to research online before you buy or go for couple known-good brands. Most of the results actually tend to be on the cheaper side (around $20 for wine, around $35 for liquor).

Digital cables, like HDMI and USB. If they meet the spec, they should operate identically.

ETA: It's a digital signal: either it works or it doesn't. There's no "higher quality" version of the same image. Sure, if you have a 4K 120hz HDR signal you might need an HDMI 2.1 spec cable, but as long as it meets that spec, it'll either work or need to be returned. The signal won't be washed out, or crackly, or static-y (all the concerns we had with analog video cables back in the day); the signal might not work, or it might drop out from time to time, which means it doesn't meet spec.

Same with USB-C. If it doesn't charge your phone correctly, or have the transfer speeds you want, because you bought it at a Dollar Store and it isn't in spec, the problem isn't USB-C, it's the fact that the manufacturer sold you an out-of-spec cable.

HDMI cables. . The cheap ones and the expensive ones have the same specifications

Dish washer soap. Gotta rep technology connections for teaching me that not only is the powdered stuff cheaper, it's also just straight up better. Also store vs name brand shouldn't make a big difference either, at least not from my tests.

When I buy dishwasher soap now I just compare price per gram and grab the cheapest option.

Cheap pregnancy tests work just as well as expensive ones do. Theyre highly regulated either way.

Fashion accessories. For most fashion (not workwear), the expensive stuff is made from the same material and in the same factories as the cheap stuff, they just market it harder.

Body wash. It's watered-down soap. Just buy a bar of soap.

Amazon Prime. Amazon used to be space-age Sears. Now it's just Aliexpress. Fake reviews and bribery are rampant, dangerously nonfunctional products get top recommendations, used and broken products get resold as new while untouched returns get thrown into landfills, Amazon Basics violates IP, and they're putting ads in Prime Video now.

Microwaves and space heaters. The boxes may try to convince you otherwise, but the amount of heat these devices can deliver is bottlenecked by the power outlet. Every 1100W microwave is just as effective as the others. If you're paying more, it's for looks and for features you'll never use like popcorn mode.

Electronics, for most people. Most people won't get more use out of a new $1500 phone than a last-gen model from the same manufacturer for $500. Do you really want a $200 smart coffee maker, or a $20 dumb coffee maker with a $10 plug-in timer?

Software. Obligatory FOSS plug. I don't blame people for sticking to what's familiar, but if you have the time and energy to spare tinkering, most software out there has a good free or open-source equivalent these days. At least for personal use. In my use case, LibreOffice beats Microsoft Word, Photopea beats Photoshop, and Google Sheets beats Excel.

Two things that have been very relevant to me recently:

Car washes. If you want the best outcome, wash it yourself. If you're just trying to knock some grime off, the cheapest one will do. The finishing sprays don't last a week.

Also beverages when hosting a party. No need to buy name brand when store brand is half the cost and will get drank the same anyway.

Anything made by Kirkland

Phones

You don't really need an 8-core CPU and 12 gigs of RAM for making calls and browsing the web, which is what 95% of people use their phones for. Not even buying such phone for the sake of longevity is worth it since most manufacturers drop support for their phones after 5 years at most.

Video games, there's thousands for free online at itch.io and even on steam.

You can always buy games discounted if you wait, and paying for microtransation games is a recipe for wasting money.

Phones.

Youtube premium

Medicine.

I often see people say to buy the expensive toilet roll but I always go for the low end of the midrange rolls. I don't need 4ply, scented, quilted shit, I just need two pieces of paper stuck together.

There is a balance, you don't want to get the 1ply stuff you'd find in a stingy office. But just look at the label and price-per-sheet

(If you can afford it, buy a year's supply in bulk from the company)

kids

Soap. My mom and sisters always complement my hair and skin, asking what products I use. I just use 2$ Yardley bar soap for skin and hair. I also like them because they smell nicer than other cheap brands that just have a generic detergent smell.

Razors. For all shaving I use a safety razor. The initial investment is somewhat expensive but after that each blade is mere cents. Also much less wasteful. Make sure to store your used blades in an old medicine bottle to dispose of them safely (and for the garbage man's safety). Also find these to be way nicer on skin, 5 blade or whatever cartridge razors don't make a closer shave and remove and irritate skin much more.

Kitchen knives. Most cheap knives (and a lot of expensive ones) suck because of bad design. Most knives today are way too thick and chunky, to make them look more robust etc. what you need is a thin blade and a sharp, long lasting edge. Victorianox fibrox ($35) is excellent for the money and for most people you don't need any more performance. You can also use kiwi knives (10$). They are super cheap, perform well, but dull fast, a good cheap option if you know how to sharpen and hone. If you want more performance than the fibrox you can get a Japanese tojiro basic. These aren't very fancy but have excellent performance, being made of laminated vg-10 steel and having a much longer lasting edge. These are around 50$

If you cook and chop a lot and want a knife to take pride and pinnacle of performance then you'll want a hand forged Japanese knife. DO NOT fall for Japanese knife scams and do lots of research on YouTube. These will be around 200$ to 500$ (more expensive knives are for prettier, or famous blades). They are very thin, highly polished (it'll glide through food) and made of extremely sharp, extremely hard, hand forged laminated steel.

A lot of generic foods. Safeway's in-house brand, for example, has better crackers, pasta sauces, a handful of other items than the expensive name brands do. And yes, that includes Rao's. I'll never understand why that brand is so popular when Safeway Select exists and tastes better with perfectly good ingredients at a fraction of the cost.