My EDC at work where I have to wear dress clothes is a SOG Flash I (straight edge) $30
My EDC any other time I have a benchmade mini griptilian 556 that's about $75
I also have Spyderco delica 4 FFG $60, spyderco endura $60
I had a Kershaw OSO Sweet that I really like, except that it doesn't hold an edge. Once you have a really good knife that can get razor sharp, it makes all the knives with cheap steel not even worth the $10-15 they cost and, for me at least, get relegated to abusive yard tasks, a vehicle kit, emergency kit, or backup knife.
I also plan on getting a spyderco paramilitary 2 that retails for about $108. So I would say that I'm comfortable spending up to $100 on a knife that I'm actually going to carry or use. Much past that and I would just baby it and not use it for it's intended purpose.
For EDC biggest concern is size and weight. If it's too large to carry, it doesn't matter how sharp it'll get. Pocket clip has to be right, can't expose the knife too much out of the pocket, can't tear pants, etc. Blade steel is 2nd most important thing. AUS8 is the minimum for me after dealing with kershaw's 8cr13mov and it's lack of edge holding. (Kershaw changed the steel in the OSO sweet because of this) The better steels are VG-10, 154CM, and S30v. there's more exotic steel like ZDP, but you have to have some special sharpening skills with that. If you have a knife with VG-10, 154CM, and S30v, just get a FINE ceramic stone from lansky (available at Academy sports) and just lightly touch up the blade monthly and it'll stay scary sharp.
I've spend a lot of $$$ on knives and that's the "best of" summary of what I've learned.