never ever buy the cheap versions of
Desk chair - in line with the philosophy others have outlined, don't cheap out on things that separate you from the ground, a good desk chair is vital. There's several good brands, obviously DXRacer or other meme gamer chairs are typically overpriced plastic trash, but you can't really go wrong if you're a competent consumer willing to spend $200+, maybe less if buying used.
Candles - If you're going to burn candles at all, don't let it be cheap ones, really horrible for you and often times smell not as good as when you hold them up to your nose in the store.
Tupperware/food storage containers - Cheap versions will stain easily if storing something acidic like pasta sauce, or warp, or won't be dishwasher safe. Plus the added risk of putting your food in a dirty China box.
Gaming controllers - may seem obvious, but in the 2000s, even up to the early 2010s, 3rd party controllers were commonly
fine, nowadays the mega cheap 3rd party controllers are barely functional, or will break pretty quickly. I've had good luck with
8bitdo, although buying 1st party is almost always your best bet for standard use.
RAM - I've known a few people build PCs, and just buy the cheapest DDR4/5 on the part picking site they used just to have them shit out in hard-to-diagnose ways that weren't immediately obvious. This goes for all PC parts when building your own, RAM specifically seems to be one people commonly think doesn't matter, there's often times a good reason some brands are cheaper.
what food has a cheap version that is absolutely unacceptable to you?
Butter/Oils - the fats you cook with should not be cheap, avoiding boomer sperging about seed oils, even cheap versions of good oils (i.e. cheap olive oil) are a bad idea and should be avoided if your grocery budget allows
Juice - cheap juice is basically koolaid, dont drink it or feed it to white children, its often times worse than drinking a full sugar soda
Canned Fish/Meat - Nothing wrong with some of the higher end, well-canned meats and fish products, the cheap stuff is super mega cancer hell and sucks shit. Spam is great, to be clear.