There are lots of good knives for $50 or under:
-BM Griptilian (you have to look around), one of the best EDC knives out there, IMHO. 440c is a good steel and the AXIS is an excellent lock, the handles are very comfortable. You can get a Mini Griptilian if you want something smaller.
-Ka-Bar Dozier folders. I have the thumb notch folder and it is a very good knife, and it costs around $20!
-SAK. You can probably find one to suit your needs, in fact I would recommend one as a companion for whatever knife you get. Even a simple Spartan is great to have around. Tim at
www.sosakonline.com has some used SAKs in very good condition that he sells for around $7, you can't get a better deal! Plus all the money goes to charity.
-Opinel, you have lots of sizes to choose from, in stainless and carbon steel. Great cutters and dirt cheap.
-Spyderco FRN knives, the Endura, Delica, Native, Centofante III are all excellent knives with great steel (VG-10) for around $40.
-The good old Buck 110 is an excellent option, you can get it for as low as $25, or pay $60 for Cabela's S30V model (which is totally worth it, IMHO)