Fun topic, but knives might well be the tool with the most diversity.
For a cheap knife, I'd focus heavily the "best value". $50 gets you lots of options of D2 flippers if that's your jam, but you don't even have to spend that much for a good knife. I suggest:
- Ka-Bar Dozier in D2 (well, the AUS8 version is also good, but I'd choose the steel with the better edge retention unless I was worried about corrosion resistance - even then, the D2 version has a coated blade). Lightweight, very neutral handle that's comfortable for heavy use, classic drop point design. Zytel handles, lockback, high flat grind.
- Crescent low-profile pocket knife - if you want a smaller option. Might well be the best value going - this is sub $30 and also has a D2 blade. It's a flipper with bearings in the pivot. Stainless steel handles. D2 is the budget steel king - surprisingly good edge retention. It is only semi-stainless, so if you work in humid environments or sweat a lot, maybe it won't be the steel for you. Otherwise, it performs very well and it's basically the best steel you'll find on knives under $75.

- Civivi Vagabond (8CR13MOV). In this case the sum is more than the total of it's parts. I still think the blade is a good steel, but it's not a super-steel. It's stainless with good toughness. Ceramic bearings in the pivot. High flat grind with a swedge. Civivi, as someone already mentioned, is just great value overall in the budget knife space. It's the design and function of this knife that puts it over the top and you might have to hold one to realize what makes it better than a lot of others at the pricepoint. There's also upgraded models of this knife, so you can spend more on it if you want.

I'll keep going if you want. These are just ones that immediately come to mind when I think of excellent EDC knives I wouldn't mind abusing. Honorable mentions:
- Ontario Rat 1 (hard use knife)
- Byrd Cara Cara 2 (larger, lightweight and very slicey)
Once you start going above $50, it's no longer just a specs competition - now you're paying for things based on your preference. E.g. do you want the "best" blade steel for the money? Do you value a particular type of lock? Do you need a big knife or a small one? Do you want a fancy-looking knife?
I'm totally enamoured with the Kizer "Drop Bear" right now. It's what I plan to buy next (if I don't get it for Christmas

). On special at the Knifecenter for $107:
154CM blade steel, very neutral handle shape, high flat grind and a cross-bar lock. Not only is a crossbar lock very strong, but it keeps your fingers out the path of the blade when closing - which is inherently safer. Looks a lot like the Dozier to me, but with a number of upgrades.
Kershaw Leek (starts at $65, but there's a ton of variations)
You might need to give us some guidance on what size of knife you want, whether you want something gentlemanly, tactical, survival, hard use, executive, etc.
CJRB Ria has a very classic look, but it still very fidget-friendly. You can get it with their proprietary powder steel AR-RMP9 for not much over $50 (they claim D2-like edge retention with more toughness and stain protection).
You can get a WE Banter for $96 at Blade HQ right now:
Or the little brother, the Civivi Baby banter for $62:
These come in a myriad of color options. I just picked a couple at random to make the point. They're both highly regarded knives.