For an EDC folding knife, the longest blade that I'm comfortable carrying is about 3". Here are some possibilities that will fit your budget, and around 3" in blade length, with approximate retail price. First, ones that I own:
Kershaw Vapor $20
AUS-6 Stainless Blade, Stainless Steel Handle, Frame Lock
Kershaw Vapor A.G. Russell FeatherLite One Hand Knife $35
AUS-8 Stainless Blade, Zytel Handle, Modified Lock Back
A.G. Russell FeatherLite Ka-Bar Dozier Folding Hunter $20
AUS-8 Stainless Blade, Zytel Handle, Lock Back
Ka-Bar Dozier Folding Hunter Timberline TimberLite Medium Drop Point Folder $15
425 Stainless Blade, Nylon/Fiberglass Handle, Neeley Lock
TimberLite Medium Drop Point Of these, my favorite is probably the A.G. Russell FeatherLite.
Knives that I don't own (yet):
Benchmade Mini Griptilian $55
440C Stainless Blade, Noryl GTX Handle, Axis Lock
Mini Griptilian CRK&T Small Crawford Falcon $33
AUS-6 Stainless Blade, Steel/Zytel Handle, LAWKS Liner Lock
Crawford Falcon Hope this helps.
the beakman