When it comes to knives everyone should own, I think the important part is not that they are the cheapest, or best, but are most representative of type and that form a baseline for comparison. To me, inexpensive is also a function of the overall utility, as well as lifespan, or resale/regift So with that in mind,
Utility: I think to start everyone should own at least one 91mm SAK, like a huntsman, just to have an idea of how useful scissors and a saw can be.
Slicer: Everyone should own at least one opinel just to know what good slicing and easy sharpening are. Everything else should compare to that, yes there are better edge holders, but I have owned knives I would have never considered if I'd owned an opinel first.
One handed opener: I'm thinking a byrd meadowlark spyderco for a hole, added benifit is it gives you options for up/down/left/right on the clip. Not as sure on stud opener, probably a Rat-1
Assist: For assisted openers, I think one of the kershaw onions. I'm sure there are better assists, but many are worse, and I think at the end of the day, many of the worse ones are also more expensive.
Fixed: For fixed blades, I think everyone should have a basic mora, one to use for everything and beat to death. In my opinion, every other fixed blade can be compared to this. Do you want "better" steel, different geometry, sheath, egros, whatever. At the end of the day, those things should all be honestly compared to 15$ worth of plastic and stainless. In a case of, if I knew then what I know now..... I had a mora, and 12 year old me didn't know how to look after it. now I compare my other fixed blades to a mora, and have to decide, what added to their price-tag, and was it worth it. Sometimes it is. Sometimes, not so much.
Neck: Becker bk13. Again there are betters and there are worse, good price point to compare others against.
Multi: right now I think the most comprehensive entry level tool is probably the Rebar. If a rebar isn't enough tool, you can upgrade, but if you can't fit a rebar into your EDC then a multi is probably not for you. (but if its close then the juice line would be the next move)
Big beast: ka-bar kukri. doesn't get a lot of love, but makes a great chopper at its price point. there are some condors in that area that are also good, I pick the ka-bar due to a larger reputation, and more consistency.
Machete: Tramontia 16 inch latin. this will let you know where you need to go with your machete. longer, heavier, shorter, its a generalist that will also let the user develop some skills.
Ax: Fiskars. again, there are better, but at the price, you can do a lot worse.
Some other categories
Fit and finish: Any Alox Vic. that should be the standard by which all others are compared
There are a lot of other factors or things that don't fit into this category. I think everyone should own at least one combo edge to find out if it works for them. There are some great folders and fixed blades in around the 100$-150$ range that are great, but that to me is the kind of money you should know what you are getting when you spend. Beyond that, you are looking for something else. But the 10-100$ range is littered with crap, so its helpful to have a few benchmarks to compare to I think.