Monthly payments. Not just entertainment subscription devices but all kinds of stuff. Almost every product online now has a monthly cost option, a buy now pay later scheme. Another one I see a lot at the grocery store is organic/non GMO foods. They are always way more expensive but are usually the same food, and if they aren't organic will contain more pesticides without the "natural" immunity/resistance of GMOs. They aren't healthier, they don't taste any better, are worse for the environment and are much more expensive.
Second is expensive and humane meat. Most metrics these meats/eggs are graded by are so loose that they are still extremely inhumane. Unless they are from a local farm, that you can confirm are humane/free roam, just buy the cheapest meat and best marbling.
Computers. I'm a tech guy and the vast majority of people are still buying computers far more powerful than they need. Unless it's cad, programming or gaming you can use almost any computer. If you want it to be really fast install, or ask your local shit to install an SSD. Plus most reputable refurbishers will install SSDs on all laptops for sale. I recommend PC server and parts, good quality refurbishment and customer support. There may be a few dings/scratches but never severe or noticeable.
Premade/processed food. Either it's frozen meals or fast food these get expensive fast. Depending on where you live quality home cooked meals can be had for 1-3$ (based on the US). Ditch even storebought pasta sauce, it's not hard to make at home.
Wifi. Most ISPs will try to upsell you on everything but for most people an families the most you would ever need is 150-300 MBps. Also the max speed can only be reached with a hardwired Ethernet connection, WiFi speed is barely affected. If you have slow wifi use an old phone or laptop as a wifi amplifier, storebought solutions are criminally expensive.
That's enough for now but if you have more questions feel free to ask.